service: Improve creating UUIDs from string

- When UUIDs are initialized from a 128-bit UUID, they are now parsed
  from the canonical UUID string representation.

- Invalid strings now cause the UUID to be marked as invalid, rather than
  causing a crash.

- Input such as "0x180d" is now valid.

- Added the GetShortestRepresentationSize() method to use in determining whether
  a UUID is within Base BT SIG UUID domain.

Bug: 24247700

Change-Id: Id28255ec963bc6da27a8e871598016d41920b688