Refactor optimizing morph for commutative operations (#63251)

* Create "fgOptimizeCommutativeArithmetic"

And just move code from "fgMorphSmpOp" to it.

Just one diff: better comma throw propagation in an ILGEN method.

* Refactor the function

Split it into specialized variants for each operator,
delete redundant code, fix up one case of wrong typing
for a constant in the MUL -> SHIFT optimization.

One CSE diff due to different VNs because of the typing
change for the constant (int -> long).

Many text diffs: "mov x3, 5" => "mov w3, 5".

Author: SingleAccretion

src/coreclr/jit/compiler.h

@@ -6409,6 +6409,10 @@ class Compiler
     GenTree* fgOptimizeCast(GenTreeCast* cast);
     GenTree* fgOptimizeEqualityComparisonWithConst(GenTreeOp* cmp);
     GenTree* fgOptimizeRelationalComparisonWithConst(GenTreeOp* cmp);
+    GenTree* fgOptimizeCommutativeArithmetic(GenTreeOp* tree);
+    GenTree* fgOptimizeAddition(GenTreeOp* add);
+    GenTree* fgOptimizeMultiply(GenTreeOp* mul);
+    GenTree* fgOptimizeBitwiseAnd(GenTreeOp* andOp);
     GenTree* fgPropagateCommaThrow(GenTree* parent, GenTreeOp* commaThrow, GenTreeFlags precedingSideEffects);
     GenTree* fgMorphRetInd(GenTreeUnOp* tree);
     GenTree* fgMorphModToSubMulDiv(GenTreeOp* tree);
@@ -6419,7 +6423,7 @@ class Compiler
     bool fgMorphCanUseLclFldForCopy(unsigned lclNum1, unsigned lclNum2);
 
     GenTreeLclVar* fgMorphTryFoldObjAsLclVar(GenTreeObj* obj);
-    GenTree* fgMorphCommutative(GenTreeOp* tree);
+    GenTreeOp* fgMorphCommutative(GenTreeOp* tree);
     GenTree* fgMorphCastedBitwiseOp(GenTreeOp* tree);
 
     GenTree* fgMorphReduceAddOps(GenTree* tree);