JIT: Stop calling morph from CSE (dotnet#106695)

CSE cannot tolerate morph removing any defs, which many of morphs
transformations can do. We have been slowly infecting morph with more
and more checks to avoid this, but in reality CSE just should not
reinvoke morph -- the benefits of doing this are minimal.

src/coreclr/jit/compiler.h

@@ -6944,7 +6944,6 @@ class Compiler
     TypeProducerKind gtGetTypeProducerKind(GenTree* tree);
     bool gtIsTypeHandleToRuntimeTypeHelper(GenTreeCall* call);
     bool gtIsTypeHandleToRuntimeTypeHandleHelper(GenTreeCall* call, CorInfoHelpFunc* pHelper = nullptr);
-    bool gtIsActiveCSE_Candidate(GenTree* tree);
 
     bool gtTreeContainsOper(GenTree* tree, genTreeOps op);
     ExceptionSetFlags gtCollectExceptions(GenTree* tree);

src/coreclr/jit/gentree.cpp

@@ -17653,11 +17653,6 @@ bool Compiler::gtIsTypeHandleToRuntimeTypeHandleHelper(GenTreeCall* call, CorInf
     return helper != CORINFO_HELP_UNDEF;
 }
 
-bool Compiler::gtIsActiveCSE_Candidate(GenTree* tree)
-{
-    return (optValnumCSE_phase && IS_CSE_INDEX(tree->gtCSEnum));
-}
-
 //------------------------------------------------------------------------
 // gtTreeContainsOper -- check if the tree contains any subtree with the specified oper.
 //