Support proto.include_dirs

For each package in the include_dirs property a proto_library target
should be added to the BUILD file in that package and a mapping
should be added to the bp2build code, by this way a proper dependency
relationship can be established and used by bazel.

Bug: 239944064
Test: Added unit tests and manually verified include_dirs can be
properly converted to bazel and used by bazel to build the targets.

Change-Id: I50d8ee21fabcfec0a44487f6e5f3d8a3845e79c3