feat: initial changes for firebase_ios_app based on firebase_web_app

[brownoxford]

Add terraform support for Firebase iOS Apps. This PR is based on the work in #3340 (firebase_web_app) and is intended to add support for the following terraform resources:

Resources

• google_firebase_ios_app

Data Sources

• google_firebase_ios_app
• google_firebase_ios_app_config

When complete, this work fixes https://github.com/hashicorp/terraform-provider-google/issues/6520. As this is a draft PR, the entire checklist below is not yet completed.

If this PR is for Terraform, I acknowledge that I have:

• [X] Searched through the issue tracker for an open issue that this either resolves or contributes to, commented on it to claim it, and written "fixes {url}" or "part of {url}" in this PR description. If there were no relevant open issues, I opened one and commented that I would like to work on it (not necessary for very small changes).
• [ ] Generated Terraform, and ran make test and make lint to ensure it passes unit and linter tests.
• [ ] Ensured that all new fields I added that can be set by a user appear in at least one example (for generated resources) or third_party test (for handwritten resources or update tests).
• [ ] Ran relevant acceptance tests (If the acceptance tests do not yet pass or you are unable to run them, please let your reviewer know).
• [X] Read the Release Notes Guide before writing my release note below.

`google_firebase_ios_app` (beta)

`google_firebase_ios_app` (beta)
`google_firebase_ios_app_config` (beta)

[modular-magician]

Hello! I am a robot who works on Magic Modules PRs.

I have detected that you are a community contributor, so your PR will be assigned to someone with a commit-bit on this repo for initial review.

Thanks for your contribution! A human will be with you soon.

@c2thorn, please review this PR or find an appropriate assignee.

[modular-magician]

Hi! I'm the modular magician. Your PR generated some diffs in downstreams - here they are.

Diff report:

Terraform GA: Diff ( 5 files changed, 177 insertions(+)) Terraform Beta: Diff ( 8 files changed, 698 insertions(+), 2 deletions(-))

[modular-magician]

I have triggered VCR tests based on this PR's diffs. See the results here: "https://ci-oss.hashicorp.engineering/viewQueued.html?itemId=190384"