Rewrite match logic of PowerDevil runner

- Support partial matches
- Allow both translated and non-translated trigger words
- Avoid duplicating the translated strings. This can become useful in
 case we also want to add the non-translated trigger words to the
 syntaxes (once they get displayed somewhere ;))
- Get rid of QRegExp usage

FEATURE: 428193
FEATURE: 428194
FIXED-IN: 5.21