Check minversion of `test-proxy` prior to push

- [ ] Add a `minimum_proxy_version.txt` file under `eng/` of `azure-sdk-assets`
- [ ] Leverage #8020 's `pull from main` ability to check get the updated file from main
- [ ] Before a `push` operation, check running proxy version against this minimum_proxy_version file.
- [ ] Error and recommend upgrade if not newer than the target version.
- [ ] an eng/common template that can check this same file and error if the running proxy version for CI is below this minimum version.

FYI @gearama this is based on your suggestion in the just-past meeting. This is lower priority than adding a version of credscan or getting that common PR out, but we'll likely get to it pretty quick.