[base] Introduce base::PickleIterator::WithData()

...and migrate trivial cases of Pickle::WithUnownedBuffer(), now marked
as deprecated.

The new replacement in PickleIterator can also read from arbitrary
buffers but avoids instantiating base::Pickle, paving the way to
eventually remove support for Pickle instances with unowned buffers.

Change-Id: Ic7329acfb2b5136523b07c332e0af823f6403502
Bug: 479750481
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7511849
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Commit-Queue: Mikel Astiz <mastiz@chromium.org>
Owners-Override: Daniel Cheng <dcheng@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1577093}
NOKEYCHECK=True
GitOrigin-RevId: d9dfa17239460a10c563357bcce86d732ec9bd2e