ui: Refactor DisplayIdentification to use ftl::stable_hash

Replace cityHash64Len0To16 with ftl::stable_hash which can handle up to
64 bytes string instead of just up to 16.

Bug: 185536303
Bug: 194863377
Test: DisplayIdentification_test
Change-Id: I90056145033ed5798dd5f5d99884028749d5d879
3 files changed