feat: protoc-gen-scala support

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Initial implementation of protoc-gen-scala. Still need to figure out what Java dependencies are required to run this in the target stage, particularly on arm64.

[rvolosatovs]

What's the status here? Is the arm64 not supported yet? If so, how about we file an issue about it and fix up in a follow-up?

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Not ready yet, I need to block out some time for more testing and to get the version strings compatible with Renovate here. I'll test arm64 build at the same time and see if we can support it immediately or later.

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I've made progress on this and understand the build process (and the errors I was seeing) much better now. I expect we will be able to complete this PR using a different build method when this fix is merged, it doesn't look like it will take too long.

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@rvolosatovs this is finally ready. The builder will not be versioned by Renovate since Scala sbt downloads different compilers as necessary. I ended up getting help from the ScalaPB maintainers and using the original build approach, will ask for help sooner next time 😅

[rvolosatovs]

Changes look good to me, but could you drop the merge commit?
Simply squashing all the commits into one based on top of latest main would be fine as well IMO (although as a nitpick it would probably be nicer to have a separate commit for reordering of the README list first)

[strophy]

Changes look good to me, but could you drop the merge commit? Simply squashing all the commits into one based on top of latest main would be fine as well IMO (although as a nitpick it would probably be nicer to have a separate commit for reordering of the README list first)

Thanks for the clear instructions, I installed GitLens and finally think I did it correctly! 🎉

[rvolosatovs]

Great job, thanks!