Refactor muxing 2 : Remove unused code, resulting from #11903

[SarahFrench]

Follow up to #11903. Most commits in this PR are in that PR, and will 'disappear' once this PR is unblocked and ready for review. This PR has been rebased to address this!

This PR deletes all the parallel implementations of provider configuration logic. The PR #11903 stops the provider using this duplicated logic, and this PR removes that redundant code.

In future the team may want to revisit this deleted code to inform work to pulls out the SDKv2 from the codebase completely and the provider becomes 100% plugin-framework. As that is a long way in the future I think it's best to delete this code now for clarity. It will still be in version control for reference in the future.

When looking at the deleted code be wary of:

• Functions with the same name as SDK code that are functions instead of methods on a struct
  • This can limit reusability of functions, e.g: ephemeral: add google_service_account_id_token #12141 (comment)
• Functions with the same name as SDK code but don't include the same logic

Release Note Template for Downstream PRs (will be copied)

[SarahFrench]

Rebased to pull in Go rewrite

[modular-magician]

Hi there, I'm the Modular magician. I've detected the following information about your changes:

Diff report

Your PR generated some diffs in downstreams - here they are.

google provider: Diff ( 5 files changed, 3746 deletions(-))
google-beta provider: Diff ( 5 files changed, 3911 deletions(-))

[modular-magician]

Tests analytics

Total tests: 4306
Passed tests: 3899
Skipped tests: 405
Affected tests: 2

Click here to see the affected service packages

All service packages are affected

Action taken

Found 2 affected test(s) by replaying old test recordings. Starting RECORDING based on the most recent commit. Click here to see the affected tests

• TestAccApigeeDeveloper_apigeeDeveloperUpdateTest
• TestAccComputeInstanceNetworkIntefaceWithSecurityPolicy

Get to know how VCR tests work

[modular-magician]

🟢 Tests passed during RECORDING mode:
TestAccApigeeDeveloper_apigeeDeveloperUpdateTest [Debug log]

🟢 No issues found for passed tests after REPLAYING rerun.

---

🔴 Tests failed during RECORDING mode:
TestAccComputeInstanceNetworkIntefaceWithSecurityPolicy [Error message] [Debug log]

🔴 Errors occurred during RECORDING mode. Please fix them to complete your PR.

View the build log or the debug log for each test

[c2thorn]

confirmed things deleted were only used by what was also being deleted. LGTM

[SarahFrench]

Thanks, I'll go ahead and merge as I don't think there's a need for multiple approvals here vs the first PR