[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/fir/tree/tree-generator/src/org/jetbrains/kotlin/fir/tree/generator/ImplementationConfigurator.kt

@@ -484,6 +484,7 @@ object ImplementationConfigurator : AbstractFirTreeImplementationConfigurator()
                 value = "null"
                 isMutable = true
             }
+            defaultFalse("isImplicit")
         }
 
         impl(thisReference, "FirImplicitThisReference") {
@@ -495,6 +496,7 @@ object ImplementationConfigurator : AbstractFirTreeImplementationConfigurator()
             default("boundSymbol") {
                 isMutable = false
             }
+            defaultTrue("isImplicit")
         }
 
         impl(superReference, "FirExplicitSuperReference")

compiler/fir/tree/tree-generator/src/org/jetbrains/kotlin/fir/tree/generator/NodeConfigurator.kt

@@ -687,6 +687,7 @@ object NodeConfigurator : AbstractFieldConfigurator<FirTreeBuilder>(FirTreeBuild
             +stringField("labelName", nullable = true)
             +field("boundSymbol", firBasedSymbolType, "*", nullable = true, withReplace = true)
             +intField("contextReceiverNumber", withReplace = true)
+            +booleanField("isImplicit")
         }
 
         typeRef.configure {