To convert smart cast expression, now we just convert
original expression in standard way and wrap it with TYPE_OP.
Before this commit original expression was converted in different way,
that led to errors e.g. for this expression casting.
Currently FirThisReceiverExpression of instance methods are translated
to references of the class' thisReceiver,
not the method's dispatch receiver,
which causes problems with IrFrameMap::typeOf,
as the class' thisReceiver is not in the typeMap.
This commit translates non-qualified "this" references of
instance methods to references of the methods' dispatch receiver.
Mikhail Glukhikh