Prohibit using suspend functions as SAM in fun interfaces

#KT-40978 Fixed

compiler/testData/diagnostics/tests/suspendConversion/suspendConversionWithFunInterfaces.fir.kt

@@ -0,0 +1,21 @@
+// !LANGUAGE: +SuspendConversion
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+
+fun interface SuspendRunnable {
+    suspend fun invoke()
+}
+
+fun foo1(s: SuspendRunnable) {}
+fun bar1() {}
+
+fun bar2(s: String = ""): Int = 0
+
+fun bar3() {}
+suspend fun bar3(s: String = ""): Int = 0
+
+fun test() {
+    foo1(::bar1)
+    foo1(::bar2)
+
+    foo1(::bar3) // Should be ambiguity
+}