Use restriction-level-* messages in Linker::formatTemplates

The current implementation of Linker::formatTemplates only checks for
"sysop" and "autoconfirmed", and completely ignores any other protection
levels. That needs fixing.

Rather than introducing additional messages "template-protected-*" to
match template-protected and template-semiprotected, let's just use the
existing restriction-level-foo messages and wrap them in parentheses.

The old messages are kept for backwards compatability, but could
probably be considered deprecated.

Bug: 43462
Change-Id: I0c507f4ecc1921f599acbda834fa55e96388fa7b