add support for user project overrides

[modular-magician]

Original Author: @danawillow

provider: Adds new provider-level field `user_project_override`, which allows billing, quota checks, and service enablement checks to occur against the project a resource is in instead of the project the credentials are from.

[ghost]

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.

If you feel this issue should be reopened, we encourage creating a new issue linking back to this one for added context. If you feel I made an error 🤖 🙉 , please reach out to my human friends 👉 hashibot-feedback@hashicorp.com. Thanks!