[ggj][bazel][codegen] feat: add gradle assembly Bazel rules (#321)

* feat: add protobuf comment parser util

* fix: add basic proto build rules

* feat: add header comments to ServiceClient

* fix: build protoc at test time

* fix!: wrap protobuf location and process comments

* feat: add comment parsing to methods and fields

* fix: test

* feat: add protobuf comments to ServiceClient

* fix: solidify codegen method order with TypeNode/MethodArg and Comparable

* fix: clean up tests

* fix: ServiceClient member variables and method calls

* fix: ServiceStubSettings builder type

* fix: ServiceSettings Builder construction

* fix: ServiceStub callable types

* feat: java_gapic_library rule impl

* fix: remove debugging comments

* feat: add gradle assembly Bazel rules

rules_java_gapic/BUILD.bazel

@@ -0,0 +1,20 @@
+load("@bazel_tools//tools/build_defs/pkg:pkg.bzl", "pkg_tar")
+
+package(default_visibility = ["//visibility:public"])
+
+exports_files(glob(["resources/**/*"]))
+
+pkg_tar(
+    name = "gradlew",
+    extension = "tar.gz",
+    files = {
+        "resources/gradle/gradle/wrapper/gradle-wrapper.jar": "gradle/wrapper/gradle-wrapper.jar",
+        "resources/gradle/gradle/wrapper/gradle-wrapper.properties": "gradle/wrapper/gradle-wrapper.properties",
+        "resources/gradle/gradlew": "gradlew",
+        "resources/gradle/gradlew.bat": "gradlew.bat",
+    },
+    mode = "644",
+    modes = {
+        "gradlew": "555",
+    },
+)