Fix for issue 5954 - Assert 'fieldSeq != FieldSeqStore::NotAField()'
Added new method GenTree:OperIsLocalField()
Fixes DefinesLocalAddress to properly update pIsEntire when we have a LocalField node type
Fixed fgValueNumberBlockAssignment to handle a GT_COPYBLK or GT_COPYOBJ operation
where we have an incomplete field sequence for the Dst/LHS node.
We already were handling an incomplete field sequence for the Src/RHS node.
Update the dump to properly print "new uniq" whenever we issue a conservative value number.