Combine two regexes into a single one.
This saves up to 5s on large databases by reducing the number
of separate scans of the comments table before regex matching.
The combined regex is slightly more permissive than the
original two, since it allows a combination of the two
matched formats. A string that matches one of the original
regexes will match the combined regex.
The `matchMarkerComment` predicate performs badly on any codebase with
a moderately large number of comments, because the current implementation
has to first compute the Cartesian product between the set of comments
and the set of framework library comment regexes.
Instead, match first against a single regex:
the union of all framework library comment regexes.
This computes a more benign Cartesian product, the same size as the set of comments.
See inline comments for more details.
