grpclb: include META-INF/services to bazel //grpclb:grpclb

[sergiitk]

Adds missing providers to libgrpclb.jar produced by bazel's target //grpclb:grpclb.

❯ jar tf bazel-bin/grpclb/libgrpclb.jar | grep services
META-INF/services/
META-INF/services/io.grpc.LoadBalancerProvider
META-INF/services/io.grpc.NameResolverProvider

Fixes #9149
cc @SanjayVas

[SanjayVas]

Is there a test for this?

[sergiitk]

@SanjayVas depends on what you mean.

1. We do test the build, but I don't think we run Java tests for bazel builds specifically
2. If you mean verification steps to confirm the files are there - I did that, see the description. bazel-bin/grpclb/libgrpclb.jar - I built it with bazel, then confirmed the files are in the jar.

[SanjayVas]

We do test the build, but I don't think we run Java tests for bazel builds specifically

This is what I meant. Automated testing for the Bazel build to avoid bugs like this one.

[sergiitk]

@ejona86 FYI - let's consider running tests with Bazel too.