Ignore the abseil privacy manifest and bump the patch version (#1885)

It appears that on macOS when building with Xcode the latest changes
have resulted in a error when resolving `swift-protobuf` reported in
#1884.

This PR ignores the abseil privacy manifest which should fix the issue

Update versions to 1.33.2 (#1883)

Bump version number (#1878)

Build `protoc` from source (#1876)

## Motivation

In a recent addition, we included changes to provide `protoc` as a
binary target from the official releases from the upstream `protobuf`
repository. While this solved one of the largest issues in our ecosystem
where folks currently needed to install `protoc` through a system
package manager, it also introduced another set of problems that binary
targets bring with them.

## Modifications

This PR adds `protobuf` and `abseil-cpp` as a submodule to this project
and includes a new target that builds both together from source. It
includes the minimal set of files from both to successfully build
`protoc` and also passes the right compiler and linker flags to build
those warning free.

## Result

We are no longer using a binary target for `protoc` but instead build it
from source which alleviates the problems that we introduced with the
binary target.

Version bump for a release. (#1865)

The `Span` support was a _minor_ bump, so left that out of the previous
release so folks would get the assertion fix if they were only accepting
bug fixes.

Update the protoc release process. (#1863)

- Call out clicking edit.
- Ensure the protoc release doesn't get counted as the "latest" for the
repo.

Version bump to do a release. (#1860)

Version bump for a release (#1852)

Prepare for a 1.31.0 release and update docs (#1843)

# Motivations

In the previous PRs, I landed support for distributing `protoc` via this
repo which finally allows us to broadly recommend the SPM plugin.

# Modifications

This PR bumps the versions and updates the docs for the SPM plugin and a
tiny addition to the RELEASING doc to ensure the latest check is set.

# Result

Unblocking the ecosystem in broadly adopting the SPM plugin.

Fix `make_latest` from Boolean to String (#1838)