[FIR] Fix resolution of LHS of augmented assignment operator call

Resolve it like a receiver of a call.
This makes the resolution result consistent with the equivalent
function call.

The K1 difference is covered by KT-66453.

#KT-66504 Fixed

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/transformers/body/resolve/FirExpressionsResolveTransformer.kt

@@ -629,7 +629,8 @@ open class FirExpressionsResolveTransformer(transformer: FirAbstractBodyResolveT
 
         assignmentOperatorStatement.transformAnnotations(transformer, ResolutionMode.ContextIndependent)
         dataFlowAnalyzer.enterCallArguments(assignmentOperatorStatement, listOf(assignmentOperatorStatement.rightArgument))
-        val leftArgument = assignmentOperatorStatement.leftArgument.transformSingle(transformer, ResolutionMode.ContextIndependent)
+        val leftArgument = assignmentOperatorStatement.leftArgument
+            .transformAsExplicitReceiver(ResolutionMode.ReceiverResolution, isUsedAsGetClassReceiver = false)
         val rightArgument = assignmentOperatorStatement.rightArgument.transformSingle(transformer, ResolutionMode.ContextDependent)
         dataFlowAnalyzer.exitCallArguments()
 

compiler/testData/diagnostics/tests/resolve/operatorAndInfixResolve.fir.kt

@@ -59,7 +59,7 @@ fun test() {
     X()
 
     X.<!UNRESOLVED_REFERENCE!>plusAssign<!>("")
-    X += ""
+    X <!UNRESOLVED_REFERENCE!>+=<!> ""
     X<!NO_GET_METHOD!>[X]<!> += ""
 
     // Must resolve to property