Codegen generates static backing fields for object properties.
They are initialized in class constructor but some of them are final static
and such access is prohibited in specification but it's allowed in
java bytecode <= 1.8. Such access in 1.9 bytecode cause
"IllegalAccessError: Update to static final field Object.INSTANCE
attempted from a different method (<init>) than the initializer method <clinit>"
Added additional hidden field in interface companion to pass out
companion instance from <clinit>.
#KT-15894 Fixed
Mikhail Glukhikh