Add commit revision to beta branch version display (#7768)

[abstewart]

Fixes #7768 .

Description of the problem being solved:

Added logic to update_manifest.py to also store the latest commit hash (short version) in the manifest.xml file.

This is then read in in Launch.lua and used in Main.lua when the branch is "beta" to display the Rev/Hash on the lower right.

Steps taken to verify a working solution:

• Force disabled rev mode, copied the latest beta manifest.xml and added a fake hash to it, launched pob and confirmed that the hash is displayed when branch is "beta" but not when "master"

Link to a build that showcases this PR: any build on the beta branch

Before screenshot:

After screenshot:

Additional Notes

• I'm unfamiliar with how the release process / installing updates works. I believe I've made all the edits for the hash to get updated with the beta build, but it's possible I missed something.
• The recorded hash might not be the absolute latest (since it might not capture the merge commit hash), but it should always update when there's new changes.

[abstewart]

The current hash in manifest.xml doesn't exist since the commit it points to (the top one) was amended with the addition of the hash, and the hash was changed as a result. Future hashes will exist in the history as long as the change to the manifest.xml is committed on top of the history and not amended to the same commit (changing the hash).