Clean up phpcs macros and jobs (remove strict/lenient split)

If any of our repos had voting on for 'lenient' but not 'strict'
this would make sense, but that was never the case.

• Remove phpcs-lenient.
• Rename phpcs-strict to phpcs.
• Update phpcs macro to use the shell script instead of inline code.
• Remove mediawiki-core-regression-phpcs* which have been commented out in zuul-config since early 2013.
• Remove obsolete 'mediawiki-core-phpcs-*-HEAD' settings which are already covered by 'phpcs(-HEAD)?$'.
• Add 'voting: true' overrides for all strict/lenient jobs which were previously implicitly voting but are now matching the override that makes them all non-voting, so we add overrides to keep those voting.

Bug: T50420
Change-Id: I0eaf2085576165ba93ca3ace14284902d3731aea