add enrollment application UID tracking

KeyphraseEnrollmentInfo class now keeps track of the different enrollment
application UIDs. It can be queries whether a given UID matches an
existing enrollment application.

Bug: 148159858
Test: build and test that enrollment application can still enroll models
with new UID check

Change-Id: Ib60ebb259e4e3ddaa07da15e2cf55fd6099ad4d0