feat(cli): restructure subcommands

[rektdeckard]

• Renames the CLI binary and associated commands from livekit-cli to lk LK-3475
  • [x] Build from source
  • [x] Linux install script (curl -sSL https://get.livekit.io/cli | bash) must wait for GitHub release
  • [ ] macOS Homebrew formula (brew install livekit-cli)
  • [x] Install procedure updated (rektdeckard/homebrew-core]
  • [x] Regenerate formula hashes once GitHub release is live with brew bump-formula-pr livekit-cli
  • [x] Windows and other precompiled binaries (CI)
  • [x] Symlinks livekit-cli -> lk on install, and prints a deprecation warning message if the binary detects $0 is not lk
• Upgrades to urfave/cli/v3 LK-3479
• Restructures many of the commands and subcommands to be more discoverable LK-3477
• Improves a lot of the usage text

Do not merge before https://github.com/livekit/web/pull/238

[CLAassistant]

All committers have signed the CLA.

[rektdeckard]

@dennwc @davidzhao Ready for final review, I think. Couple things to note:

The Linux install script and the brew formula both rely on GitHub release artifacts, so they will come in a separate PR here and against homebrew, respectively, after this is merged and released.

Since our only means of distribution for Windows is pre-built binaries, I haven't done anything besides change the name of the binary we build. Those users will probably figure it out for themselves when they upgrade (though we might want to consider packaging for choco and/or winget).

And of course, all of this should line up with https://github.com/livekit/web/pull/238