BREAKING CHANGE: The values of Wasm locals, stack, and globals are now
represented as objects instead of holding the (primitive) values
directly, and SIMD128 values are no longer represented as Uint8Arrays.
The DWARF extension has been prepared for this breaking change.

The new `WasmValue` comes with `type` and `value` properties that hold
its contents. The motivation here is that this is a more extensible
approach. In case of SIMD128, the `value` property holds the canonical
string representation, which has the additional advantage that these
values can be compared with `===` (and `==`).

This partially reverts https://crrev.com/c/2614428, the main difference
here being that WasmValue is now a proper JSObject that can be exposed
on the DebugEvaluate proxy API.

Screenshot: https://imgur.com/rcahNKM.png
Bug: chromium:1170282, chromium:1071432, chromium:1159402
Change-Id: Iea304e3680775123c41deb4c3d172ac949da1b98
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2643384Reviewed-by: Philip Pfaffe <pfaffe@chromium.org>
Reviewed-by: Zhi An Ng <zhin@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#72570}