[SLP][NFC] Add pre-commit tests for merged inputops flag propagation (#236366)
Add two tests covering flag propagation for the merge-input-operands
transform: one where the fmul lanes carry different fast-math flags and
one where the mul lanes carry different integer wrap flags. Both record
the current vectorization, so a later patch shows the effect of merging.
Co-authored-by: Balakrishna Bandlapalli <bbandlap@gmail.com>
Co-authored-by: Cursor <cursoragent@cursor.com>