This is a reland of 80843eda

Original change's description:
> [torque] Allow storing to bitfield structs that are stored in Smis
> 
> This change:
> 1. Updates the Torque compiler to allow direct access to bitfields that
>    are packed within Smi values, which previously would have required a
>    separate untagging step,
> 2. Updates JSRegExpStringIterator to represent its flags in Torque,
> 3. Adds reduction cases in MachineOperatorReducer for when the input to
>    a branch or the left-hand side of a Word32Equals is based on a 64-bit
>    shift-and-mask operation which has been truncated to 32 bits, as is
>    the case in the code generated by step 1, and
> 4. Adds a reduction case in MachineOperatorReducer to remove an extra
>    Word64And operation added by step 1.
> 
> Bug: v8:7793
> Change-Id: Ib4ac2def6211b3cae6be25a8b2a644be5c7d6d3f
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2119225
> Commit-Queue: Seth Brenith <seth.brenith@microsoft.com>
> Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#67290}

Bug: v8:7793
Change-Id: I783b6ec080042fec0e922927f6675dede458a072
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2159731Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67305}