Implement rolling upstream updates

[AndrewL97]

Mirror-bot is unsustainable for our small team (Kosh is the only person doing it, because he beautiful man)

New solution

New branch - "Upstream-Staging" Every month (week if PR is automated):

• Merge Master into Upstream-Staging
• Pull TG into Upstream-Staging, with full commit history.
• Fix any conflicts and hopefully catch any bugs that arise
• Tag Master branch with format YY.MM.AB.R (Year, month, Alpha/Beta, Revision)- i.e 21.12.A.2 is the second revision for the alpha release, in December 2021
• Make a PR from Upstream-Staging to Master, SQUASH (full history is kept in U-S branch)

To get to this stage, we need to

• Nuke Mirror-Bot
• Nuke Mirror PRs
• Configure Github Actions for rolling weekly updates (optional)
  • This should make instability more manageable
• Hopefully nothing else

[AndrewL97]

@Koshenko FYI, ticket for visibility Will aim to get this done first thing in the morning - work Christmas party tonight 🥳