[FIR] Add NOTHING_TO_INLINE diagnostic

compiler/fir/analysis-tests/testData/resolve/cfg/postponedLambdas.kt

@@ -1,5 +1,5 @@
 // !DUMP_CFG
-inline fun foo(vararg x: Any) {}
+<!NOTHING_TO_INLINE!>inline<!> fun foo(vararg x: Any) {}
 
 fun test(a: Any, b: Any, c: Any) {
     foo(a, { "" }, b)

compiler/fir/analysis-tests/testData/resolve/extendedCheckers/RedundantVisibilityModifierChecker.kt

@@ -6,7 +6,7 @@ fun f() {
     LocalClass().foo = 1
 }
 
-internal inline fun internal() {
+internal <!NOTHING_TO_INLINE!>inline<!> fun internal() {
     f()
 }