Bug: UUID class accepts uppercase input

Should help tracking down "AbstractQuery.php: Did not load root post <CapitalizedUUID>" exceptions.
Should additionally fix up any invalid capitalized uuid's read from cache so they don't trigger
failures elsewhere.

Bug: 71377
Change-Id: I6b2fbf05918d7554768b701638ac6186ceca2150
Merge "Bug: UUID class accepts uppercase input"