Add test to preserve behaviour

It's important to have ambiguity in these cases to introduce overload
 resolution by suspend-modifier without breaking changes in future

 Relates to #KT-23610

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

@@ -0,0 +1,19 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+
+fun foo(x: () -> Int) {}
+fun foo(x: suspend () -> Int) {}
+
+fun usualCall(): Int = 42
+suspend fun suspendCall(): Int = 42
+
+// it's important to have ambiguity in these cases to introduce overload resolution by suspend modifier in future
+fun test1() {
+    <!AMBIGUITY!>foo<!> { usualCall() }
+    <!AMBIGUITY!>foo<!> { suspendCall() }
+}
+
+// candidate without suspend conversions is more specific
+fun test2(f: () -> Int, g: suspend () -> Int) {
+    foo(f)
+    foo(g)
+}

compiler/testData/diagnostics/tests/suspendConversion/overloadResolutionBySuspendModifier.kt

@@ -0,0 +1,19 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+
+fun foo(x: () -> Int) {}
+fun foo(x: suspend () -> Int) {}
+
+fun usualCall(): Int = 42
+suspend fun suspendCall(): Int = 42
+
+// it's important to have ambiguity in these cases to introduce overload resolution by suspend modifier in future
+fun test1() {
+    <!OVERLOAD_RESOLUTION_AMBIGUITY!>foo<!> { usualCall() }
+    <!OVERLOAD_RESOLUTION_AMBIGUITY!>foo<!> { <!ILLEGAL_SUSPEND_FUNCTION_CALL!>suspendCall<!>() }
+}
+
+// candidate without suspend conversions is more specific
+fun test2(f: () -> Int, g: suspend () -> Int) {
+    foo(f)
+    foo(g)
+}

compiler/testData/diagnostics/tests/suspendConversion/overloadResolutionBySuspendModifier.txt

@@ -0,0 +1,8 @@
+package
+
+public fun foo(/*0*/ x: () -> kotlin.Int): kotlin.Unit
+public fun foo(/*0*/ x: suspend () -> kotlin.Int): kotlin.Unit
+public suspend fun suspendCall(): kotlin.Int
+public fun test1(): kotlin.Unit
+public fun test2(/*0*/ f: () -> kotlin.Int, /*1*/ g: suspend () -> kotlin.Int): kotlin.Unit
+public fun usualCall(): kotlin.Int