LanguageTool 2.1 standalone

- Use now the standalone languagetool package

- Add additional languagetool-server and languagetool-gui exec scripts

Closes #19328.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>
brew-test-bot: use Jenkins env, add step.passed?
Fix Formula#installed_prefix logic

Due to the precedence of "and" relative to "||", this was not working as
intended; but because #version influences #prefix, the outcome was still
correct. So we can simplify this method quite a bit, and take the
opportunity to share code with #prefix.
brew-test-bot: shorten Jenkins env SHA-1s.
brew-test-bot: don't repeat SHA-1 if identical.