Analysis API: fix call resolve inside plusAssign target

^KT-50864 fixed

analysis/low-level-api-fir/testdata/getOrBuildFir/calls/compoundAssignOnVal_lhs.txt

@@ -1,6 +1,6 @@
 KT element: KtNameReferenceExpression
 FIR element: FirPropertyAccessExpressionImpl
-FIR source kind: DesugaredCompoundAssignment
+FIR source kind: KtRealSourceElementKind
 
 FIR element rendered:
 R|<local>/l|

analysis/low-level-api-fir/testdata/getOrBuildFir/expressions/insidePlusAssignTarget.kt

@@ -0,0 +1,6 @@
+// WITH_STDLIB
+// LOOK_UP_FOR_ELEMENT_OF_TYPE: org.jetbrains.kotlin.psi.KtCallExpression
+
+fun foo(x: MutableMap<Int, MutableList<String>>) {
+    x.getOrPut(1) { <expr>mutableListOf<String>()</expr> } += "str"
+}

analysis/low-level-api-fir/testdata/getOrBuildFir/expressions/insidePlusAssignTarget.txt

@@ -0,0 +1,6 @@
+KT element: KtCallExpression
+FIR element: FirFunctionCallImpl
+FIR source kind: KtRealSourceElementKind
+
+FIR element rendered:
+R|kotlin/collections/mutableListOf|<R|kotlin/String|>()