[FIR] Introduce FirAssignExpressionAltererExtension

This extension can be used to override resolution of assign statements
  with custom statement

compiler/fir/semantics/src/org/jetbrains/kotlin/fir/resolve/diagnostics/ConeDiagnostics.kt

@@ -16,7 +16,6 @@ import org.jetbrains.kotlin.fir.symbols.FirBasedSymbol
 import org.jetbrains.kotlin.fir.symbols.impl.*
 import org.jetbrains.kotlin.fir.types.ConeKotlinType
 import org.jetbrains.kotlin.fir.types.FirTypeRef
-import org.jetbrains.kotlin.fir.types.renderForDebugging
 import org.jetbrains.kotlin.name.ClassId
 import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.resolve.calls.tower.CandidateApplicability
@@ -233,3 +232,8 @@ private fun describeSymbol(symbol: FirBasedSymbol<*>): String {
         else -> "$symbol"
     }
 }
+
+class ConeAmbiguousAlteredAssign(val altererNames: List<String?>) : ConeDiagnostic {
+    override val reason: String
+        get() = "Assign altered by multiple extensions"
+}