[7.2.0] Extract Bazel registry creation into a SkyFunction (#22138)

This gets rid of an ad-hoc cache maintained in `RegistryFactoryImpl` and
prepares for making registries aware of hashes stored in the lockfile.

Work towards #20369

Fixes https://github.com/bazelbuild/bazel/issues/22052

.

Closes #22040.

PiperOrigin-RevId: 626307340
Change-Id: I34b428553f7169c72ed7dddd2fe3ea5e6dca2a97

Co-authored-by: Fabian Meumertzheim <fabian@meumertzhe.im>