Specify `secret_id` as a variable in `gh-runner-mig-vm`

[tcordeu-backcountry]

TL;DR

Currently the secret-id is hard coded to "gh-token" in https://github.com/terraform-google-modules/terraform-google-github-actions-runners/blob/b1f90cc6540105c081a176f0ff3a89de9e36bafc/modules/gh-runner-mig-vm/main.tf#L78C15-L78C25.
This makes it impossible two run two instances of this module on the same GCP project.

Can we make that configurable? I can help with a PR for this.

Thank you!

Terraform Resources

Detailed design

Just adding secret_id to the accepted variables for this module would be enough.

Additional information

No response