[terminal] Consider "main.cs(20,5)" to be a single clickable word (#19004)

[terminal] Consider "main.cs(20,5)" to be a single clickable word

First, adding unit tests for the regexes because I'm not certain how
these regexes are _intended_ to work, and unit tests work nicely as
demonstrations of intended behaviour.

The comment string, and the regex itself, seem to imply that
"main.cs(20,5)" is supposed be a single "word" (for the purposes of
being clicked on)... but the regex doesn't actually work like that. This
PR makes it work :)

(I don't know _why_ "word with an optional `(\d+,\d+)` on the end"
doesn't match the full string, while "word with a required `(\d+,\d+)`
on the end" _does_ match the full string - aren't regexes supposed to
match as much as possible, so it should take the optional extra whenever
the extra exists? Either way, "word with a required (\d+,\d+), or word
by itself" has the correct behaviour, as demonstrated by the unit test)

Release Notes:

- N/A