Most interface calls are preceded by a reachability check, such that we
only generate code if the current instruction is actually reachable.
This is particularly important for Liftoff (TurboFan would throw out
dead parts of the graph anyway).

In order to speed up this check, this CL introduces a boolean flag
directly on the {WasmFullDecoder}. This avoids checking whether an error
has been set *plus* checking the reachability of the top-most control
block.

This provides 5-6% speedup on Liftoff compilation locally.

R=thibaudm@chromium.org

Bug: v8:10576
Change-Id: Idcff623fb9c23473b06ebf91b3caee65cc6ca28b
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2230521Reviewed-by: Thibaud Michaud <thibaudm@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68200}