As part of an effort to prepare the Recorder interface for general use,
we had to make some changes to the way the existing Wasm Events are
being used. In particular,
  - it is more fitting to use a ElapsedTimer than a TimedScope to
    measure the durations in src/wasm/module-[decoder|instantiate].cc
  - we want to rename the wall_clock_time_in_us field to duration_in_us
    for clarity.

Because these Wasm events are already being instantiated in chromium,
renaming the field requires a two-step change. This is the first of
those changes.

Change-Id: If1b2990f7645616a59fc21d07ac10bf00701c0e5
Bug: v8:11109
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2518619Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Emanuel Ziegler <ecmziegler@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#71053}