The main goal is to untangle Liftoff from the TF-based wasm compiler,
but since the AccessBuilder does not simplify anything but rather adds
complexity I also removed it from the wasm compiler.
Instead, we now bottleneck all offset computations through the new
ObjectAccess helper.

R=titzer@chromium.org

Bug: v8:6600
Change-Id: I362b7b889d68e89da8c30d3fad7b5bab07bee5c8
Reviewed-on: https://chromium-review.googlesource.com/1204090Reviewed-by: Ben Titzer <titzer@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55646}