CI for btfhub-archive PRs

[brycekahle]

I think it could be valuable to have CI checks for btfhub-archive PRs. This would allow us to enforce some quality standards, such as:

1. no folder structure in the tarball
2. file naming within the the tarball
3. maybe checking the BTF itself, to ensure it was generated with the correct pahole arguments

I'm not sure there is a way to do this without having files in-tree of the btfhub-archive repo. This means consumers would need to ignore a .github folder (or equivalent).

[geyslan]

This could be an issue to btfhub-archive repo.