Switch to HexEncoding from ByteStringUtils

Migration in preparation for deletion of ByteStringUtils.

Bug: 124232146
Test: build only
Exempt-From-Owner-Approval: Already approved in upstream.
Change-Id: I2cb09da5ec5296799e03bab812b7fb29452a623e
(cherry picked from commit 2344ec4f7563ce3739627255b143a14061a5f9a9)
2 files changed