Implement worker support for `GenerateDataBindingBaseClasses`

[arunkumar9t2]

• Moved GenerateDataBindingBaseClasses to ResourceProcessorBusyBox since Android databinding classes were already a dependency there.
• ProcessDatabinding is already part of ResourceProcessorBusyBox but it was not enabled in persistent_android_resource_processor expansion flag. Added that as well.

This change is multiplex compatible and probably could use expansion flags as done here https://github.com/bazelbuild/bazel/pull/15950.

Results: In a synthetic generated project with 30 modules here https://github.com/arunkumar9t2/bazel-playground, the worker can be turned off/on with .bazel.sh build //android/databinding_workers:android_data_binding --strategy=GenerateDataBindingBaseClasses=[sandboxed|worker] and worker is about 9 to 10% faster.