Make WasmFeatures a proper class which uses an EnumSet under the hood.
This way, it inherits all behaviour of EnumSet like comparison, merge,
etc.
Accesses change from being simple field access into the struct to
actually bit tests in the EnumSet.

R=mstarzinger@chromium.org

Bug: v8:10019
Change-Id: I768f92b90ac0294156f4482defba5ce00bc70165
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1934334
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65184}