KT-16264 Forbid usage of _ without backticks

Forbid underscore-only (_, __, ___, ...) names as callees and as types.

If CHECK_TYPE directive is on, filter out UNDERSCORE_USAGE_WITHOUT_BACKTICKS messages.

compiler/testData/codegen/box/multiDecl/UnderscoreNames.kt

@@ -10,5 +10,5 @@ fun box() : String {
 
     val (`_`, c) = A()
 
-    return if (a == 1 && b == 2 && _ == 1 && c == 2) "OK" else "fail"
+    return if (a == 1 && b == 2 && `_` == 1 && c == 2) "OK" else "fail"
 }

compiler/testData/codegen/box/multiDecl/forRange/UnderscoreNames.kt

@@ -31,7 +31,7 @@ fun doTest(): String {
     }
 
     for ((_, `_`) in C(2)..C(4)) {
-        s += "$_;"
+        s += "$`_`;"
     }
 
     return s