This is a first step towards supporting unwrapped WasmObject objects on
JavaScript side.

In addition this CL
1) introduces Representation::WasmValue which is used for all WasmObject
   fields exposed to JavaScript side.
2) adds creation of meaningful DescriptorArrays for WasmObject's Maps.

Bug: v8:11804
Change-Id: I4afcd39da5cb77b659943da54a2ca34d13bcc9bd
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2912776
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74744}