FIR2IR: read & set dispatch & extension receivers

NB: this commit includes receiver-based assertions yet failing for some tests

compiler/testData/ir/irText/stubs/javaEnum.fir.txt

@@ -3,7 +3,6 @@ FILE fqName:<root> fileName:/javaEnum.kt
     FIELD PROPERTY_BACKING_FIELD name:test type:<root>.JEnum? visibility:public [final,static]
       EXPRESSION_BODY
         GET_FIELD 'FIELD IR_EXTERNAL_JAVA_DECLARATION_STUB name:ONE type:<root>.JEnum? visibility:public [final,static]' type=<root>.JEnum? origin=GET_PROPERTY
-          receiver: GET_OBJECT 'CLASS ENUM_CLASS name:JEnum modality:FINAL visibility:public superTypes:[kotlin.Enum<<root>.JEnum>]' type=kotlin.Unit
     FUN DEFAULT_PROPERTY_ACCESSOR name:<get-test> visibility:public modality:FINAL <> () returnType:<root>.JEnum?
       correspondingProperty: PROPERTY name:test visibility:public modality:FINAL [val]
       BLOCK_BODY