mediawiki-core-phpunit-* made concurrent

Updates MediaWiki PHPUnit jobs to be runnable concurrently:

    mediawiki-core-phpunit-api
    mediawiki-core-phpunit-databaseless
    mediawiki-core-phpunit-misc
    mediawiki-core-phpunit-parser

This would make tests fails whenever there is a race condition. A few
occurrences have been fixed already:

* parser jobs had a race condition, creating a file named Foobar.svg in
  the temp directory causing parralel jobs to fails.

* the mw-install-sqlite.sh script was deleting *.sqlite in the tmpfs
  directory. Fixed and deployed slave script change
  https://gerrit.wikimedia.org/r/#/c/102149/

bug: 47063
Change-Id: I78fd99fa15731b4eb6d4c3ef1d573e972443aaa2