Pages Query: use $text search or prefix search

[ikreymer]

Instead of regex search on url and title:

• If search string starts with https:// or http://, do a prefix search on URL
• Otherwise, do a $text search on title, sort by match score.

[tw4l]

Overall makes sense, see inline question about RAM usage of text indices, and also looks like the corresponding test needs to be updated to match new behavior (I'm guessing it's due to how $text indices tokenize that we don't quite the result we expected in that test, perhaps due to punctuation in titles?)