[MLIR][SCF] Add canonicalization pattern to fold away iter args of scf.forall (#90189)

-- This commit adds a canonicalization pattern to fold away iter args of
scf.forall if :-
   a. The corresponding tied result has no use.
   b. It is not being modified within the loop.

Signed-off-by: Abhishek Varma <avarma094@gmail.com>