Handle proto.include_dirs in bp2build for CC

Soong's proto.include_dirs becomes the -I path for aprotoc cpp code
generation. This does not translate well to Bazel because it runs this
action in a sandbox. Even if we construct an -I path, the .proto files
will not be there. This CL attempts to handle this kind of dependency
automatically via bp2build.

For this hypothetical example
```
foo.proto # contains `import bar.proto"
Android.bp # cc_library {srcs:"foo.proto", p.include_dirs:["subdir"]},

subdir/bar.proto

```

Implementation details for CcProtoGen of foo
- Glob the labels of .proto files for each includeDir, and create a
  proto_library that encapsulates them.
- Since Bazel poses a contraint that proto_library target needs to be
  in the same pacakge as the .proto file, the proto_library might be created
  in a subdirectory with an import_prefix
- Add bar's proto_library as transitive deps of foo's cc_proto_library.
  This will be added to -I during aprotoc. We cannot add them to `deps`,
  otherwise bar's symbols will be statically linked into foo's .a
  file.

Implementation details for clang compile of foo
At the end of CcProtoGen, we have converted foo.proto
to .cpp/.h files. To compile them to .a files, we need the .h files
generated from bar.proto. Soong specifies this at the
top-level cc_library soong module, so add those deps as the
implementation deps for clang compile.

(Will add support for java in a follow-up CL)

Test: go test ./bp2build
Test: built some internal modules that were previously blocked by this
Bug: 285140726

Change-Id: I7e1f9f0d1b1ba916a7ba8278f6cfb342b381d695