[Sampling profiler] Reland "Rename NativeStackSampler to StackSampler"

Drops the 'Native' part of the StackSampler name in support of a
future cross-platform sampler implementation that delegates to
platform-specific code at a lower level of abstraction.

This is a reland of f7d1ff11e2d4621e8a903535d71c2a86b7e2df1f with
a test compilation fix.

Bug: 909957
Change-Id: I54a9dcaac13a451fe1bea0f37e5e8b4edf1a7bf1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1537747
Auto-Submit: Mike Wittman <wittman@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Reviewed-by: oysteine <oysteine@chromium.org>
Commit-Queue: oysteine <oysteine@chromium.org>
Cr-Commit-Position: refs/heads/master@{#644388}
26 files changed