rubocop.yml: reduce Max LineLength.

Fixed the formulae in homebrew/core. Slowly but surely...

cli/parser: add and use more helpers.

extend/string: match multiline make variables

dependency_collector: make resource dep available at test-time too

There are formulae that use resource blocks for stuff that is needed in
test blocks. If a resource is a `.zip` archive, one needs `unzip`
utility in `PATH` to extract it, but its only available at build-time,
so one observes an error like that for example:

```
==> brew test psftools --verbose
Testing psftools
==> Downloading https://www.zone38.net/font/pc8x8.zip
Already downloaded: /github/home/.cache/Homebrew/downloads/ea5f6a485687368ff5bc99e4cc43a49b06e081baa51a97ee6ddcd8d1b82d7963--pc8x8.zip
==> Verifying ea5f6a485687368ff5bc99e4cc43a49b06e081baa51a97ee6ddcd8d1b82d7963--pc8x8.zip checksum
unzip -o /github/home/.cache/Homebrew/downloads/ea5f6a485687368ff5bc99e4cc43a49b06e081baa51a97ee6ddcd8d1b82d7963--pc8x8.zip -d /tmp/d20200304-21389-ui0wr0
Error: psftools: failed
undefined method `shelljoin' for nil:NilClass
```

Of course this issue affects Linux the most, because of higher
probability that the system lacks `unzip` for example.

With this commit, all resource guessed dependencies should be available
at build and test time.

docs/Homebrew-on-Linux.md: Use the bash installer

python: Use literal "python" for virtualenv path

workflows/tests: cleanup actions.

Tweak GitHub Actions code to be more consistent.

keg: handle more exceptions on uninstall.

python: Fix error in virtualenv_install_with_resources

Fixes https://github.com/Homebrew/brew/issues/7110

Fixes #7115.

search: add separate flag for formulae

change `export PATH` to `add-path` for github actions

build: bump zeitwerk from 2.2.2 to 2.3.0 in /Library/Homebrew

API: supply additional data for requirements

Fix for when version is nil

Bumps [zeitwerk](https://github.com/fxn/zeitwerk) from 2.2.2 to 2.3.0.
- [Release notes](https://github.com/fxn/zeitwerk/releases)
- [Changelog](https://github.com/fxn/zeitwerk/blob/master/CHANGELOG.md)
- [Commits](https://github.com/fxn/zeitwerk/compare/v2.2.2...v2.3.0

)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

brew: remove most traces of python@2

build: bump zeitwerk from 2.2.2 to 2.3.0 in /docs

Bumps [zeitwerk](https://github.com/fxn/zeitwerk) from 2.2.2 to 2.3.0.
- [Release notes](https://github.com/fxn/zeitwerk/releases)
- [Changelog](https://github.com/fxn/zeitwerk/blob/master/CHANGELOG.md)
- [Commits](https://github.com/fxn/zeitwerk/compare/v2.2.2...v2.3.0

)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>