Import `importlib.metadata` as `importlib_metadata` if stdlib
version is recent enough (python >= 3.10). Otherwise import
the `importlib_metadata`, but explicitly verify the version
of `importlib-metadata` dist, which must be >= 4.6. This
version is needed for extended functionality, such as `group`
and `name` keyword arguments having been added to the
`entry_points()` function.

Add `importlib-metadata >= 4.6` to requirements if python < 3.10.

Add `packaging` >= 20.0 to requirements; used for parsing of
version and requirements strings.

Replace the `PYINSTALLER_NO_PYWIN32_FAILURE` environment variable
set by `setup.py` into more general `_PYINSTALLER_SETUP_PY`, which
now covers the following run-time dependencies in the `compat`
module:
* `importlib_metadata` on python < 3.10
* `pywin32-ctypes` on Windows

This "setup.py mode" prevents `compat` from trying to import
afore-mentioned run-time dependencies, which may not be present
when PyInstaller wheels are being built (nor are required for
the `compat` functionality used by the `setup.py`).

Switch to `importlib.metadata` (or `importlib_metadata`) for entry
point enumeration during the discovery of hook directories.

Add two test that try to query metadata that was collected from
(non-zipped) .egg. In such cases, we collect the EGG-INFO directory
containing the metadata under its original parent directory
(the package_name-version.egg) to prevent clashes between
metadata from multiple .egg sources. The first test queries the
metadata using `pkg_resources`, while the second uses
`importlib.metadata` / `importlib_metadata`.

It seems that `pkg_resources` is able to discover metadata
collected from eggs as long as the parent directory of the
.egg directory is in `sys.path`. This is automatically true in
our case, because we collect the  `package_name-version.egg`
directories (that contain `EGG-INFO` metadata directories) into
`sys._MEIPASS`.

In contrast, `importlib.metadata` does not seem to pick up
such metadata unless the `.egg` directories themselves are
in `sys.path`. So have the bootstrap script scan for directories
with `.egg` suffix and append them so `sys.path`.

Port metadata collection (`copy_metadata` hook utility function)
from `pkg_resources` to `importlib.metadata` and `packaging`.
The latter is required for parsing package requirements and
evaluating markers to exclude the requirements that are not
applicable to the running python version and/or platform.

Simplify the metadata destination handling code; the only
special case we need to care about is EGG-INFO directory in
.egg  directories, where we need to preserve the parent
directory instead of collecting into top-level application
directory.

`importlib.metadata` seems to properly resolve the path to
egg-info files used by Debian/Ubuntu packages, so we can also
remove the legacy name/path handling.

Have the remaining hook utility functions that make use of
`pkg_resources` import it locally, so we can port them one-by-one.

Port the `get_installer` helper from `pkg_resources` to
`importlib.metadata`. Requires python >= 3.10 or equivalent
`importlib-metadata` (>= 4.6) due to use of the
`packages_distributions()` convenience function.

Since the `copy_metadata` calls in `_metadata_from` now use
`importlib.metadata` instead of `pkg_resources`, we now need
to handle the `importlib.metadata.PackageNotFoundError` instead
of `pkg_resources.PackageNotFoundError`.

Use `compat.importlib_metadata` to properly resolve
`importlib.metadata` vs `importlib_metadata` regardless if the
latter is available on python > 3.10, where our `compat` prefers
the stdlib version.

The only use for `modulegraph.replacePackage` is for the `_xmplus`
module from python2-era PyXML package. Remove the function and
associated code.

In contemporary python, namespace packages should be handled without
having to resort to parsing the *-nspkg.pth files.

Rework the support for legacy setuptools-based namespace packages
and port it to `importlib.metadata`.

The legacy namespace packages are regular packages with `__init__.py`
that calls deprecated  `pkg_resources.declare_namespace(__name__)`.

We could get rid of this altogether once we are fine with not
supporting legacy namespace packages that are split across
multiple locations. Currently, our test suite contains such an
example (e.g., `test_import.py::test_nspkg1`). The code has been
refactored so that dropping support will also be easier.

To properly support legacy namespace sub-packages that are split
across different locations, we need to scan the metadata of all
dists, similarly to how it was done by the original `pkg_resources`
based implementation. However, within the life-time of a module
graph instance, we can perform the scan only once, and cache the
results.

Port the entry-point scan for test discovery from `pkg_resources`
to `importlib.metadata`.

Replace `is_module_satisfies` with `check_requirement`, which
uses `packaging` to parse the requirement and check the version
against the optional specifier(s), and `importlib.metadata` to
query the dist version.

Keep `is_module_satisfies` as an alias for `check_requirements`
to maintain compatibility with existing hooks (from the contrib
hooks repository) that call the function with only the
`requirement` string. The calls with additional `version` and
`version_attr` arguments will not work anymore, nor will the
fall back to checking module's version when the specified
requirement is not satisfied.

Have the @requires test decorator use `check_requirement`.

Update hooks in this repository to use `check_requirement`
instead of `is_module_satisfies`.

Update Qt hook utilities, where we need to account for the
fact that `check_requirement` does not attempt to fall back
to checking module's version (which in this case was
undesirable and had to be worked around).

Have `collect_all` look up the dist name for the given package
name before attempting to call `copy_metadata` and
`requirements_for_package`. This fixes the collection (and
spurious warnings) for cases when dist name does not match the
importable/package name.

Adjust the behavior of `collect_data_files` when the `include_py_files`
flag is enabled: collect only `.py` and `.pyc` files, and never
collect `.pyc` files from the `__pycache__` directory.

Update the description to note that module collection mode is
preferable way of ensuring that source .py files are collected
(in addition or in lieu to byte-compiled modules in PYZ).

Adjust the `test_collect_data_all_included` accordingly.

Remove `requirements_for_package` hook utility, which was
used by `collect_all`. Consequently, the latter does not include
the top-level modules of metadata-declared requirements among the
returned hidden imports anymore.