Resolve cross account user icon validation.

Resolves a vulnerability found with the cross account user icon
validation in StatusHint and TelecomServiceImpl (when registering a
phone account). The reporter found that an uri formatted as `userId%`
isn't parsed properly with the existing reference to Uri.encodedUserInfo.

Bug: 376461551
Bug: 376259166
Flag: EXEMPT bugfix
Test: atest TelecomServiceImplTest
Change-Id: I25614ead889501f4553ed2b42b366e09a47b0c9f
Merged-In: I25614ead889501f4553ed2b42b366e09a47b0c9f