Update some Parcelables to send Strings UTF-8.

An earlier CL with benchmarks has shown that sending strings as UTF-8
is 50% faster for US-ASCII strings, and still 68% faster for complex
strings referencing higher Unicode planes.  (So an improvement in
both cases!)

Since code across the OS still makes heavy assumptions about Parcel
strings typically being UTF-16, we need to carefully migrate
Parcelables by hand, which is what this CLs begins doing.

This is a purely mechanical refactoring with no functional changes.

Bug: 154436100
Test: manual
Exempt-From-Owner-Approval: trivial refactoring
Change-Id: Ia9e581efd7c40269342b7528ca07363deb843c0f