feat: support multiple firebase sites

[glasnt]

With #56, will help resolve #45

This change uses Firebase Hosting Sites, which allows for a multiple deployments per project.

Suffixes are appended to the project ID to entire global uniqueness.

[glasnt]

TestSimpleExample 2023-04-28T06:20:41Z retry.go:99: Returning due to fatal error: FatalError{Underlying: error while running command: exit status 1; 
Error: Error creating Site: googleapi: Error 404: Requested entity was not found.

  with module.dynamic-python-webapp.google_firebase_hosting_site.client,
  on ../../firebase.tf line 24, in resource "google_firebase_hosting_site" "client":
  24: resource "google_firebase_hosting_site" "client" {
}

I was getting this in testing this code yesterday, and if I reapplied the terraform, I'd get a 409 error, but the site was created.

[grayside]

LGTM with comments. Thank you for continuing to push through on making multi-deploy per project work!

[grayside]

question: Since both sections below have an init step, what is this init-all doing?

[glasnt]

I'm not sure, this was copied from https://github.com/GoogleCloudPlatform/terraform-google-secure-cicd/blob/main/build/int.cloudbuild.yaml#L31 as a presumed 'best practice' (note: only example I could find)

[glasnt]

I'm chatting with tf blueprint maintainers around best practices here, tbd

[grayside]

discussion: At first I found this variable's presence on the Cloud Run Jobs mysterious, and wondered if we should have inline comments linking to usage. But I'm not sure we want to try maintaining a list like that to be comprehensive. This is one of those pieces that hand-off to future maintainers might lose track how to handle changes.

[glasnt]

I've added links to the script usage, which might help, but happy to do more