Fix link prefix and trail regexp handling

* Bug 56255: https://gerrit.wikimedia.org/r/#/c/91425/ added a linkprefixcharset entry in
the site info instead of the occasionally-broken linkprefix regexp. Use that
to construct the prefix regexp.

* Update base configs with the new linkprefixcharset entry

* Bug 52855: Convert PHP to JS syntax unicode code points

Bug: 56255
Bug: 52855
Change-Id: Ia7d27f7700046ce5e83c0065cfbb29b4f370ca64