Fixes #6300

People are using this instead of adjusting their PATH.

`brew cask` no longer supports the `search` command and was removed from
the `homebrew/brew-cask` documentation. However, it's still in the
`brew` man page for `brew-cask`.

Remove search from the man page.

Matching what's already been done for `brew info`.

It's always seemed a bit pointless to me that we have both of these
commands. Given we're doing more and more to recommend (and eventually,
safely, automatically run (see #4760) `brew cleanup` let's roll their
functionality into a single command.

Let's document these so people know who the leadership team behind the
project is.

Use brew man to generate manpages, and then copy them to the repo.

This reverts commit 4475651b.

Address the confusion in #4015.

These specify that they are needed by the test block. This can be
combined with `:build` to ensure that this formula isn't uninstalled
by `brew test-bot` when running `test do` blocks on our CI.

and improve wording or formatting where necessary.