Delete `GTF_INX_REFARR_LAYOUT`

[jkotas]

This flag should be no longer needed. Deleting it is causing unexpected assembly diffs that need to be investigated. More context: #32521 (comment)

[jkotas]

cc @ivdiazsa

[AndyAyersMS]

Looks like one source of collision is GTF_IND_NONFAULTING.

[AndyAyersMS]

When morphing GT_INDEX nodes, we were inadvertenly setting GTF_IND_NONFAULTING
for the GT_IND subtree for ref type arrays, because GTF_IND_NONFAULTING has
the same value as GTF_INX_REFARR_LAYOUT.

This turns out to be safe since in general there is an upstream bounds check to
cover the null check from the indexing operation, so the fact that we were claiming
the GT_IND can't fault is ok.

A no diff change would remove the flag and then modify fgMorphArrayIndex
to set GTF_IND_NONFAULTING for ref type arrays with bounds checks:

    // If there's a bounds check, the the indir won't fault.
    if (bndsChk && (tree->gtType == TYP_REF))
    {
        tree->gtFlags |= GTF_IND_NONFAULTING;
    }

    tree->gtFlags |= GTF_EXCEPT;

Removing GTF_INX_REFARR_LAYOUT and adding change above gives a no-diff change.

But there's no good reason to limit the above to ref type arrays
and no good reason to OR in GTF_EXCEPT when there are bounds checks.

Once we do the more general fix we see diffs, so might as well further
clean up by removing the odd related constraint in the importer under
REDO_RETURN_NODE.