Fix "**" precedence in AntPathMatcher comparator

Prior to this commit, "**" and "*" pattern elements had
the same priority when comparing two patterns.
So when comparing several patterns, the computed order was:
1- /hotels/{hotel}/bookings/{booking}
2- /hotels/**
3- /hotels/{hotel}/bookings/{booking}/customer/{customer}

This commit updates the comparator so that patterns ending
with "**" (a.k.a "catch-all" patterns) are less specific than
the others; in the previous example, the 2nd pattern would
then end up last.

This commit also optimizes the comparator implementation.

Issue: SPR-6741