[FIR] fix resolution ambiguities between weakly compatible expect and actual

There is a corresponding example inside the stdlib,
see `kotlin.text.startsWith`.

JVM and common counterpart are weakly-compatible
as the actual declaration has default arguments,
which results in `ExpectActualCompatibility.Incompatible.ActualFunctionWithDefaultParameters`

This commit allows such cases.

^KT-61732 fixed

compiler/fir/tree/src/org/jetbrains/kotlin/fir/declarations/ExpectActualAttributes.kt

@@ -11,6 +11,7 @@ import org.jetbrains.kotlin.fir.symbols.impl.FirFunctionSymbol
 import org.jetbrains.kotlin.fir.symbols.impl.FirRegularClassSymbol
 import org.jetbrains.kotlin.fir.symbols.lazyResolveToPhase
 import org.jetbrains.kotlin.resolve.multiplatform.ExpectActualCompatibility
+import org.jetbrains.kotlin.resolve.multiplatform.isCompatibleOrWeaklyIncompatible
 
 private object ExpectForActualAttributeKey : FirDeclarationDataKey()
 
@@ -26,6 +27,13 @@ fun FirBasedSymbol<*>.getSingleExpectForActualOrNull(): FirBasedSymbol<*>? {
     return expectForActual?.values?.singleOrNull()?.singleOrNull()
 }
 
+fun FirBasedSymbol<*>.getSingleCompatibleOrWeaklyIncompatibleExpectForActualOrNull(): FirBasedSymbol<*>? {
+    val expectForActual = expectForActual ?: return null
+    val compatibleOrWeakCompatible: List<FirBasedSymbol<*>> =
+        expectForActual.entries.singleOrNull { it.key.isCompatibleOrWeaklyIncompatible }?.value ?: return null
+    return compatibleOrWeakCompatible.singleOrNull()
+}
+
 val FirBasedSymbol<*>.expectForActual: ExpectForActualData?
     get() {
         lazyResolveToPhase(FirResolvePhase.EXPECT_ACTUAL_MATCHING)