fix some failures.

It appeared that we have many trees where we generate unique VN for rhs and don't inform `fgValueNumberBlockAssignment` about it.
For example, for
```
N005 ( 10,  8) [000033] -A--G---R---              *  ASG       struct (copy)
N004 (  3,  2) [000031] D------N----              +--*  LCL_VAR   struct<eightByteStruct, 8> V01 loc1         d:2
N003 (  6,  5) [000030] n---G-------              \--*  IND       struct
N002 (  3,  3) [000043] ------------                 \--*  ADDR      byref
N001 (  3,  2) [000044] -------N----                    \--*  LCL_VAR   struct<largeStruct, 32> V00 loc0         u:6 (last use)
```
we will generate unique rhs but then `fgValueNumberBlockAssignment` will still try to work it as with a non-unique one.

src/coreclr/jit/valuenum.cpp

@@ -7286,7 +7286,6 @@ void Compiler::fgValueNumberBlockAssignment(GenTree* tree)
                                 // will be handled in `VNPairApplySelectorsAssign`, here we care only about
                                 // `LCL_VAR structX = (*)LCL_VAR structY` cases.
                                 JITDUMP("    *** Different struct handles for Dst/Src of COPYBLK\n");
-                                assert(ClassLayout::AreCompatible(rhsVarDsc->GetLayout(), lhsVarDsc->GetLayout()));
                                 isNewUniq = true;
                             }
                         }