fix(ts_proto_library): require explicit srcs to copy (#617)

[alexeagle]

Backport this commit to 2.x branch

• Example on bazel failing when 2 ts_proto_library are in a single BUILD file

error: Error in directory_path: directory_path rule '_logger_pb.d.ts_dirpath' in package 'examples/proto_grpc' conflicts with existing directory_path rule

• fix: explicit files_to_copy for multiple ts_proto_lib

• fix(ts_proto_library): require explicit srcs to copy

The hack of using a glob over the srcs causes a collision when there is more than one ts_proto_library in a bazel package. The resulting error doesn't give a clue what fix is required.

• chore: docgen

• fix: docs

[aspect-workflows[bot]]

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