TeamCity: Add project for testing the provider functions feature branch

[SarahFrench]

Partially addresses https://github.com/hashicorp/terraform-provider-google/issues/17451

This PR adds a new project in TeamCity to enable testing of provider-defined functions:

• Tests the FEATURE-BRANCH-provider-functions branch in the downstreams on a schedule
• Allows testing provider-defined functions from PRs in the MM upstream forks
• Runs those tests with an alpha release of TF 1.8.0 while leaving our nightly tests etc unaffected (using the default version of Terraform - 1.2.5)

Release Note Template for Downstream PRs (will be copied)

[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.

Terraform GA: Diff ( 6 files changed, 139 insertions(+), 4 deletions(-))

[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.

Terraform GA: Diff ( 6 files changed, 141 insertions(+), 6 deletions(-))

[SarahFrench]

A deployed version of this config can be found here : https://hashicorp.teamcity.com/project/TerraformProviders_SarahTestingFeatureBranchProjects?projectTab=overview&mode=builds

I've only entered the creds for interacting with the VCR project, so only the MM ones will work currently!

Here's a build that runs tests for the functions package against the MM upstream branch from when I added the project_from_id function.

Edit: this is not functional anymore because the creds were revoked

[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.

Terraform GA: Diff ( 6 files changed, 142 insertions(+), 7 deletions(-))