Improved support for short codes in Coalescer.

Use ShortNumberInfo to identify shortcodes and apply more basic matching for them; without this short codes like '5555' and '55555' would match due to being a SHORT_NSN_MATCH even though they should not match.

Also removed the PhoneNumberUtil argument from DialerPhoneNumberUtil's constructor as it was always PhoneNumberUtil.getInstance(). (This allowed me to do a similar thing for ShortNumberInfo.getInstance()).

TEST=unit
Bug: 71586485
Test: unit
PiperOrigin-RevId: 193288929
Change-Id: Ia16c78e7eee5e0912d3913660952b9ee32713731