v20241018-152153

Enable non-org autoscaler to read scale-config from any repo (#5767)

Enable putting scale-config in test-infra, even for non-organization
runners. Before, only scale-configs for organization-scoped runners
could be put in arbitrary repos

Significant change:
- `scale_config_repo` no longer defaults to test-infra. You now _have_
to specify a value if you're using org runners. Non-org runners will
default to the job's repo. pytorch-gha-infra and ci-infra will need to
be updated accordingly.

Testing: Deployed these changes to LF canary, terminated all lf-c
instances, and verified that creating a new pull request there would
still result in instances getting provisioned