Fixes Homebrew/homebrew#32710.

 - use literal syntax
 - escape interpolated variables
 - remove intermediate variables
 - remove unnecessary capture

Closes Homebrew/homebrew#31203.

This reverts commit e81b82cc725ede00c1292a50a076bb8a652ccecd.

This reverts commit 338a451a47c884eb9ca96d7b0023417a1eaa4d3d.

This reverts commit f96ed45fe19855d0f8acc37d5d77d16d607dfce3.

This reverts commit 91be9f5344d5931ddae6e4f905c18a607fa9e9f1.

Closes Homebrew/homebrew#32472.

As this is something we support and update.

This means that taps root and `cmd` directories are added to the PATH.

This should enable migration of some of our contributed commands into
taps (e.g. `homebrew-boneyard`) and make it easy for third parties to
be able to maintain these. It might also make stuff easier for existing
tools like e.g. `brew-cask` and `boxen`.

Closes Homebrew/homebrew#32471.

This is currently still very messy and we probably want to work out the
best way to declare what parts of our DSL/what files are "public".

Still, even if this is a WIP I'd rather get something committed sooner
rather than later and start iterating on this as a replacement for
`example_formula.rb` and the formula cookbook.

To test:
```bash
cd $(brew --prefix)/Library/Homebrew && \
  rdoc formula.rb requirement.rb utils.rb &&\
  open doc/index.html
```

Closes Homebrew/homebrew#32470.

This reverts commit f9c8b5e1da7ac09c85a6ebf9a94624bb9c60bed5.

Closes Homebrew/homebrew#32609.
Closes Homebrew/homebrew#32613.

This reverts commit f05d29e3fd0d056b78da6a0b0247e64f91014e04.

This reverts commit 2885a92612173f480303b03da1da739eb68550d7.

This reverts commit 6319cac687fa722a1d005fe056e0dac22d91ef9c.

Only the keys of the hashes are used, so we can just use arrays and
comments instead.

Closes Homebrew/homebrew#32224.

Before this change, audit would detect commented-out lines
containing the string 'DATA' as if there were no commenting.
Then it could complain, e.g., problem "'DATA' was found, but no
'__END__'", which would be a false alarm in that circumstance.

Closes Homebrew/homebrew#32568.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>