Introduce Unit-conversions for simple arguments

compiler/testData/diagnostics/tests/unitConversion/unitConversionForAllKinds.kt

@@ -0,0 +1,16 @@
+// !LANGUAGE: +UnitConversion
+// !DIAGNOSTICS: -UNUSED_PARAMETER -UNUSED_EXPRESSION
+
+fun foo(f: () -> Unit) {}
+fun <T> fooGeneric(f: (T) -> Unit): T = TODO()
+
+fun bar(): String = ""
+fun createCall(): () -> Int = TODO()
+
+fun test(g: () -> String, h: (Float) -> String) {
+    foo(::bar)
+    foo { "something" }
+    foo(g)
+
+    <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Float")!>fooGeneric(h)<!>
+}