Fix winget tag specification

Avoid an extra `dotnet restore` during the `dotnet publish` commands in
`layout.sh` when building the macOS installer.

For some reason, the CI machines (and sometimes locally) hang during
this step with:

```
Building Installer.Mac
Copying uninstall script...
Microsoft (R) Build Engine version 16.10.0-preview-21181-07+073022eb4 for .NET
Copyright (C) Microsoft Corporation. All rights reserved.

  Determining projects to restore...

```

Avoiding the restore during publish should be OK since the hosting
Installer.Mac.csproj project will have already built (and restored)
packages for the dependent projects.

Avoid extra restore in macOS installer creation (fix CI hangs)

Copied and refreshed the Bitbucket development doc from the Git Credential Manager for Windows project.

Issue-267 Add fingerprint header, to autodetect Bitbucket DC instances.

a small "how to use" tweak

This change replaces Python scripts we were calling from the
`release-apt-get` pipeline with inline scripts. It also adds support for
releasing to Ubuntu repositories hosted at
http://packages.microsoft.com/ (hosting location for Microsoft's
official apt/yum repos). This allows users to install via apt-get on
Hirsute/Bionic. Details to configure appropriate repos can be found
here:

https://docs.microsoft.com/en-us/windows-server/administration/Linux-Package-Repository-for-Microsoft-Software).

Update apt-get workflow to publish to official bionic/hirsute repos

Updating README.md with instructions for apt-get setup and install
for Ubuntu Bionic and Hirsute.

We are currently using 'Release tag' to describe the required input
to our `workflow_dispatch` trigger. This is inaccurate - this field
actually requires a 'Release id', which I discovered when testing
GCM Core `apt-get` deployments yesterday. Updating so that the
description doesn't confuse folks running the workflow for a release
that is not 'latest'.

Add instructions for `apt-get` install to `README`

Add a stable anchor for linking to Linux instructions

When creating the plaintext credential store root directory, create it
with permissions such that only the owner/user can read/write/execute,
and not the group or other users.

This only impacts newly created store directories; existing directories
do not have their permissions modified.

Only applies to POSIX platforms.

Clarify that is necessary to run `git-credential-manager-core configure`.

Introduce the concept of another layer of settings (lowest precedence;
default values only) below the existing environment variable and Git
configuration file mechanisms.

Implement on Windows using the Registry, under key:

  HKLM\SOFTWARE\GitCredentialManager\Configuration

Add documentation about the new enterprise/registry settings.

Clarify that is necessary to run git-credential-manager-core configure.

Updated ISSUE_TEMPLATE from version to --version

Clarify that the new registry settings are aimed at enterprises and
system administrators, _and_ that the settings are at the lowest
precedence; they can always be overridden by the user.

Dynamically skip the macOS Keychain read/write/delete test if the
Keychain is in a "strange" state.

There is an unknown issue that the keychain can sometimes get itself
in where all API calls result in an errSecAuthFailed error. The only
solution seems to be a machine restart; not possible in CI!

The problem has plagued others who are calling the same Keychain APIs
from C# such as the MSAL.NET team - they don't know either. It might
have something to do with the code signing signature of the binary
(our collective best theory).

It's probably only diagnosable at this point by Apple, but we don't
have a reliable way to reproduce the problem.

Add ability to specify default settings values from the registry on Windows

Create plaintext credential store directory with safer permissions

If GCM_GPG_PATH is specified, it is assumed to be the path to the GPG
executable used by `pass` and will throw an exception if it is not found.
If GCM_GPG_PATH is _not_ specified, GCM Core will attempt to find the
correct GPG executable by mimicking the behavior (currently) used by `pass`
(that is, first searching for `gpg2`, then falling back on `gpg` if `gpg2` is
not found).

Add option for `GCM_GPG_PATH` environment variable (Linux-only)