Switch from Byte.toHexString() to HexEncoding equivalents.

Bug: 124232146
Test: build only
Exempt-From-Owner-Approval: Cherry-picking OWNERS approved internal version
Merged-In: Id244e5247eb87c67446cbd65eb5d320f3617b8cd
Change-Id: Id244e5247eb87c67446cbd65eb5d320f3617b8cd