Parse arguments with commander instead of yargs-parser

[ecraig12345]

Among other things, this allows using built-in help functionality. The downside is commander is in some ways less flexible/capable than yargs, so some workarounds are required to minimize breaking changes.

• (initial abandoned attempt) Replace yargs-parser with commander for CLI option parsing #1192
• Switch to commander for arg parsing #1303
• Use class-extension-based commander approach #1306
• Define commands with commander #1307
• Better commander help formatting #1308
• Improve option organization and help text #1310

[ecraig12345]

Commands are still orchestrated by cli.ts, but that would be another migration effort with less benefit, unless the entire options merging was moved into BeachballCommand or something.