ByteBuffer: allow chaining of AppendOrDie()

In some of our calling contexts, it would be more
convenient to initialize a const ByteBuffer in a
single expression.

To that end:
- Update ByteBuffer, to allow chaining of calls
  to AppendOrDie().
- Updating existing uses of ByteBuffer, to make
  use of this new capability (where appropriate).

Bug: 32317095
Test: ./runtests.sh (on angler)
Change-Id: I39585b204ee6cc112ebe233670be8a9ab30d584b
5 files changed