Prefer using plaintextParams instead of rawParams where possible

Prefer using plaintextParams instead of rawParams where possible

Using Message::rawParams() is something that should immediately
jump out as scary. While it's perfectly safe to do something like
wfMessage( 'foo' )->rawParams( $userControlledVar )->text() and
escape later, mixing the safe type of rawParams with the
dangerous type makes it more likely someone will miss something
when checking for security.

To reduce the likelyhood of confusion, prefer ->plaintextParams
for such cases, as it can be seen to be safe at a glance.

Change-Id: Ib067eb08ec934779ae743751306f1a0397bdf71c