Merge two deprecation diagnostics into one DEPRECATION

This also fixes weird suppressions in user code: instead of
«@Suppress("DEPRECATED_SYMBOL_WITH_MESSAGE")» you should now use
«@Suppress("DEPRECATION")»

compiler/testData/diagnostics/tests/thisAndSuper/superInExtensionFunctionCall.kt

@@ -1,6 +1,6 @@
 // No supertype at all
 class A1 {
     fun test() {
-        <!SUPER_CANT_BE_EXTENSION_RECEIVER!>super<!>.<!DEPRECATED_SYMBOL_WITH_MESSAGE!>identityEquals<!>(null) // Call to an extension function
+        <!SUPER_CANT_BE_EXTENSION_RECEIVER!>super<!>.<!DEPRECATION!>identityEquals<!>(null) // Call to an extension function
     }
-}
+}