add tidy warning for unrecognized directives

This makes tidy warn on the presence of any directives it does not recognize.

There are changes in compiletest because that file used "tidy-alphabet" instead of "tidy-alphabetical".

src/tools/compiletest/src/runtest.rs

@@ -32,7 +32,7 @@ use crate::{ColorConfig, json, stamp_file_path};
 mod debugger;
 
 // Helper modules that implement test running logic for each test suite.
-// tidy-alphabet-start
+// tidy-alphabetical-start
 mod assembly;
 mod codegen;
 mod codegen_units;
@@ -47,7 +47,7 @@ mod run_make;
 mod rustdoc;
 mod rustdoc_json;
 mod ui;
-// tidy-alphabet-end
+// tidy-alphabetical-end
 
 #[cfg(test)]
 mod tests;