test: migrate remaining public-api tests to Bazel (#22639)

We now create npm packages to cover all the public api assertions in tools/public_api_guard.
We no longer depend on ts-api-guardian from npm - it is now stale since the repository was archived.
There is no longer a gulp task to enforce or accept the public API, this is in CircleCI as part of running all bazel test targets.

PR Close #22639

packages/platform-server/testing/BUILD.bazel

@@ -4,7 +4,6 @@ load("//tools:defaults.bzl", "ng_module")
 
 ng_module(
     name = "testing",
-    testonly = 1,
     srcs = glob(["**/*.ts"]),
     module_name = "@angular/platform-server/testing",
     deps = [