This is needed to make protobuf/bazel package minimal for other proto rules.
Keep 4 public bzl files in upb/bazel. They end up under protobuf/bazel, and they are legitimately used by other repositories.
Move upb_proto_library_internal/* under bazel/private. Those are utilities used in the rules. Moving them one level deeper makes protobuf/bazel package clean for other rules.
Move build_defs.bzl and amalgamation under /upb/bazel. Those are utilities used in the build.
Move lua.BUILD and python* uner /python/dist. Those are used in the WORKSPACE dependency setup.
PiperOrigin-RevId: 621442236
This change moves almost everything in the `upb/` directory up one level, so
that for example `upb/upb/generated_code_support.h` becomes just
`upb/generated_code_support.h`. The only exceptions I made to this were that I
left `upb/cmake` and `upb/BUILD` where they are, mostly because that avoids
conflict with other files and the current locations seem reasonable for now.
The `python/` directory is a little bit of a challenge because we had to merge
the existing directory there with `upb/python/`. I made `upb/python/BUILD` into
the BUILD file for the merged directory, and it effectively loads the contents
of the other BUILD file via `python/build_targets.bzl`, but I plan to clean
this up soon.
PiperOrigin-RevId: 568651768