This is a reland of 408e7240
Change: Allow CSA load elimination accross code comments

Original change's description:
> [torque] typed context slot access
>
> This introduces a new type Slot<ContextType, SlotType> that is used
> for enum values used to access context slots.
> Together with new types for the various custom contexts used in
> Torque, this results in fairly type-safe access to context slots,
> including the NativeContext's slots.
>
> Drive-by changes:
> - Introduce a new header file to specify headers needed for
>   generated CSA headers, to reduce the amount of includes specified
>   in implementation-visitor.cc
> - Port AllocateSyntheticFunctionContext to Torque.
>
> Bug: v8:7793
> Change-Id: I509a128916ca408eeeb636a9bcc376b2cc868532
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2335064
> Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
> Reviewed-by: Seth Brenith <seth.brenith@microsoft.com>
> Cr-Commit-Position: refs/heads/master@{#69249}

Bug: v8:7793
Change-Id: I1fe100d8d62e8220524eddb8ecc4faa85219748d
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2339462Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69264}