[rush] Expose commandToRun option to command-line.json config

[arikon]

Summary

Let's expose commandToRun option from IBulkScriptActionOptions to command-line.json config.
So we could define incremental and non-incremental commands (like build and rebuild), invoking the same script, on the project level.

[apostolisms]

This will possibly be covered by this #2300.

Can you please provide more details?

[elliot-nelson]

Closing -- you can now override behavior of incremental and non-incremental command versions, as well as redefine them as phased operations. (Please reopen if there's specific functionality still missing that you were looking for!)