This is a reland of d11a0648

Original change's description:
> [torque] Implement safe initialization of classes through hidden structs
> 
> Initialization of classes now happens atomically at the end of the
> class constructor only once all of the values for the class' fields
> have been fully computed. This makes Torque constructors completely
> GC safe, e.g. hardened against allocations or exceptions in
> constructors.
> 
> As part of this change, make the 'this' parameter for method calls
> explicit rather than implicit.
> 
> Drive by: add validation to check for duplicate field declarations
> 
> Bug: v8:7793
> Change-Id: I8b5e85980d6a103ef9fc3262b76f6514f36ebf88
> Reviewed-on: https://chromium-review.googlesource.com/c/1411252
> Commit-Queue: Daniel Clifford <danno@chromium.org>
> Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#58979}

Bug: v8:7793
Change-Id: Ia8c23a36a661a73b5dc34437efd514a7c13a1ae8
Reviewed-on: https://chromium-review.googlesource.com/c/1426840Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Commit-Queue: Daniel Clifford <danno@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59005}