cli: fix type signature of to_kegs_to_casks

Add `--update` option to `brew vendor-gems`.

Fix `brew audit --tap=<tap>`.

Support `--cask` flag in `brew uninstall`.

Support casks in `brew audit`.

Improve `brew install --quiet`

Big Sur cleanup

Preparations for merging `brew cask audit` into `brew audit`.

Remove `HOMEBREW_BIG_SUR_TESTING` variable as it is no longer needed.

- Suppress (some more) warnings when doing `brew install --quiet`
- Clarify `man brew` output that we don't suppress all warnings
  for all commands with `--quiet`

While I was doing this I noticed references to the (soon to be
deprecated) `brew switch` so:
- remove these references in `install` output
- remove a reference in the documentation
- add a comment to remind me to deprecate `brew diy`, too

Fixes #9179

upgrade: show upgradeable dependents during dry run

Don't create `package.json` in current directory.

Unset `HOMEBREW_BAT` in tests.

Fix tests failing locally.

sorbet: Update RBI files.

Enable `Performance/ConstantRegexp` cop.

Autogenerated by the [sorbet](https://github.com/Homebrew/brew/blob/master/.github/workflows/sorbet.yml) workflow.

cli/named_args: don't convert to taps.