Returns a new instance with URL patterns from the current instance ("this") and
the "other" instance as follows:
If there are patterns in both instances, combine the patterns in "this" with
the patterns in "other" using PathPattern.combine(PathPattern).
Compare the two conditions based on the URL patterns they contain.
Patterns are compared one at a time, from top to bottom. If all compared
patterns match equally, but one instance has more patterns, it is
considered a closer match.
It is assumed that both instances have been obtained via
getMatchingCondition(ServerWebExchange) to ensure they
contain only patterns that match the request and are sorted with
the best matches on top.