We want to eventually move the profiling functionality out of V8 as library,
this patch exposes TickSample and its APIs in v8-profiler.h so that when
embedders use library, they can have more details.

Minor change: Rename tick-sample.[h|cc] to simulator-helper.[h|cc].

BUG=v8:4789
LOG=N

Review-Url: https://codereview.chromium.org/2105943002
Cr-Commit-Position: refs/heads/master@{#37564}