[NAN] Remove builder API using String to translate to byte[] [DO NOT MERGE]

Per API review: String accessor was not needed (duplicate, semantics
not accurate, trivial use-case).

Bug: 31470256
Test: unit tests & integration (sl4a) testing.
Change-Id: I1c33d06887afc88c112d9e095121b9f18af9c06c
2 files changed