[Fleet Console] Commit hello world code.

Boilerplate copied from https://chromium.googlesource.com/infra/luci/luci-go/+/refs/heads/main/examples/k8s/helloworld as a starting point for prototyping.

Added a few changes to the Makefile to make it possible to deploy a Cloud Run service to fleet-console-prototype.

Bug:360173512
Change-Id: I13fbf4a58d52f898a070c1f8e377bf39558a0c18
Reviewed-on: https://chromium-review.googlesource.com/c/infra/experimental/+/5817679
Commit-Queue: Tiffany Zhang <zhangtiff@chromium.org>
Reviewed-by: Justin Suen <justinsuen@google.com>