feat(common): new HttpClient API

HttpClient is an evolution of the existing Angular HTTP API, which exists
alongside of it in a separate package, @angular/common/http. This structure
ensures that existing codebases can slowly migrate to the new API.

The new API improves significantly on the ergonomics and features of the legacy
API. A partial list of new features includes:

* Typed, synchronous response body access, including support for JSON body types
* JSON is an assumed default and no longer needs to be explicitly parsed
* Interceptors allow middleware logic to be inserted into the pipeline
* Immutable request/response objects
* Progress events for both request upload and response download
* Post-request verification & flush based testing framework

packages/common/BUILD

@@ -4,6 +4,7 @@ load("@io_bazel_rules_typescript//:defs.bzl", "ts_library")
 ts_library(
     name = "common",
     srcs = glob(["**/*.ts"], exclude=[
+      "http/**",
       "test/**",
       "testing/**",
     ]),