bazel: Support java_export by adding maven_coordinates to targets

What version of gRPC-Java are you using?

1.50.2

What is your environment?

OSX

What did you expect to see?

The pom file generated from a java_export when using GRPC includes GRPC dependencies rather than inlining them into the generate jar file.

What did you see instead?

The pom file does NOT include a grpc dependency. The generate jar includes directly grpc classes. For example: io/grpc/Attributes.java, io/grpc/util/AdvancedTlsX509KeyManager.java, io/grpc/stub/AbstractAsyncStub.java

Steps to reproduce the bug

1. Create a java bazel project following the canonical example
2. Add a java_export rule, see below.
3. Run the publish rule: bazel run --define "maven_repo=file://$HOME/.m2/repository" //export_test:export_test.publish
4. Examine the resulting pom file and artifact

• jar tf ~/.m2/repository/com/example/exporttest/0.0.1/exporttest-0.0.1-sources.jar|less
• less ~/m2/repository/com/example/exporttest/0.0.1/exporttest-0.0.1.pom

5. Observe that protobuf and grpc dependencies are omitted from the pom file
6. Observe that protobuf and grpc classes are in the jar file

java_export(
    name = "export_test",
    maven_coordinates = "com.example:exporttest:0.0.1",
    runtime_deps = [
        "//export_test_lib",
        "@maven//:com_google_protobuf_protobuf_java",
        "@maven//:com_google_protobuf_protobuf_java_util",
        "@maven//:io_grpc_grpc_api",
        "@maven//:io_grpc_grpc_core",
        "@maven//:io_grpc_grpc_protobuf",
        "@maven//:io_grpc_grpc_stub",
    ],
)

Workaround

Simply removing IO_GRPC_GRPC_JAVA_OVERRIDE_TARGETS, added here, seems to work fine.

Alternatively, perhaps someone could set the maven_coordinates tags so that java_export knows which artifacts to reference!