TimeTicks::HighResolutionNow is identical to TimeTicks::Now since 2018
(https://crrev.com/c/997153), but the declaration still has a wrong
comment about a non-existing DCHECK.
In order to avoid confusion, remove the redundant method and just use
TimeTicks::Now everywhere.

Drive-by: Make IsHighResolutionTimer "inline" instead of "V8_INLINE"
because it will only be called once anyway.

R=mlippautz@chromium.org

Bug: v8:12425
Change-Id: I31dc65f8c1ac910862e070e60e928054d4921154
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3439909Reviewed-by: Yang Guo <yangguo@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/main@{#78944}