feat(common): introduce experimental `httpResource` (#59876)

`httpResource` is a new frontend to the `HttpClient` infrastructure. It
declares a dependency on an HTTP endpoint. The request to be made can be
reactive, updating in response to signals for the URL, method, or otherwise.
The response is returned as an instance of `HttpResource`, a
`WritableResource` with some additional signals which represent parts of the
HTTP response metadata (status, headers, etc).

PR Close #59876