cli,storage: add emergency ballast

[jseldess]

PR: cockroachdb/cockroach#66893

From release notes:

Added an automatically created, on by default, emergency ballast file. This new ballast defaults to the minimum of 1% total disk capacity or 1GiB. The size of the ballast may be configured via the --store flag with a ballast-size field, accepting the same value formats as the size field. Also, added a new Disk Full (10) exit code that indicates that the node exited because disk space on at least one store is exhausted. On node start, if any store has less than half the ballast's size bytes available, the node immediately exits with the Disk Full (10) exit code. The operator may manually remove the configured ballast (assuming they haven't already) to allow the node to start, and they can take action to remedy the disk space exhaustion. The ballast will automatically be recreated when available disk space is 4x the ballast size, or at least 10 GiB is available after the ballast is created. [#66893][#66893]

[taroface]

@rmloveland This was covered by your PR that I reviewed, right?

[rmloveland]

Yes, closed by #11932