Handle RC cut failure

Action item from [requiem/doc/postmortem475066](http://requiem/doc/postmortem475066).

In `14.1.0-rc.0` for tooling, the RC failed to release due to a new package, so the `main` branch was never bumped to `14.2.0-next.0`. This left the repository in an inconsistent state, where `14.1.x` had the `14.1.0-rc.0` release which is ahead of the `14.1.0-next.x` release previously in `main`. `ng-dev` appropriately discovered this issue and failed on subsequent executions lest it do the wrong thing, but this required a manual version bump in `main` to address which is not obvious.

The proper solution is probably to just _not_ fail RC releases, but that's tricky to guarantee. If and when an RC cut fails, we should define some kind of fallback behavior such as:
* Doing the `main` bump anyways (which might be risky given that RC branch could be in a weird state).
* Roll back the RC version bump (also might be risky for the same reason).
* Print a message that `main` and RC are now conflicting and what options the caretaker has to resolve it (least risky automation, but caretakers can get confused or potentially do the wrong thing in response).