Self-hosted runner failing when trying to use new Gitlab runner authentication flow

[SamKnightGit]

The current code for acquiring a runnerToken attempts to fetch a token in the following order:

1. Use the legacy endpoint (/projects/<projectPath>
2. Use the new runner authentication endpoint (/user/runners)

However, in the legacy path, the legacy endpoint can return undefined for the token when legacy runner tokens are not enabled. This leads to the null check entry to the new endpoint code path failing.