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.
Before this commit, we had two methods to do generally the same synthetic thing.
It's an attempt to keep only one of them.
Accessor symbols are generated in Java use-site member scopes,
at this place we know better whether we are in Java class or not.
However, we have to do this at every use-site level, which is relatively slow.
Also we could encounter problems when accessor function is overridden in Kotlin,
and accessor symbol can still contain reference to Java accessor.
Juan Chen