[FIR] Store expressions of receivers inside candidates instead of ReceiverValue

This is needed because of mutable nature of receiver values: implicit
  receiver values can be modified because of smartcasts, but in candidate
  we need to store snapshot of receiver in the form it was at the beginning
  of the resolution

^KT-58823 Fixed

compiler/testData/codegen/box/smartCasts/smartcastOnImplicitDispatchReceiver.kt

@@ -1,5 +1,4 @@
 // TARGET_BACKEND: JVM
-// IGNORE_BACKEND_K2: JVM_IR
 // ISSUE: KT-58823
 // FILE: Base.java