Remove registered_lints field from Session

It only exists to pass some information from one part of the driver to
another part. We can directly pass this information to the function that
needs it to reduce the amount of mutation of the Session.

compiler/rustc_interface/src/interface.rs

@@ -479,7 +479,6 @@ pub fn run_compiler<R: Send>(config: Config, f: impl FnOnce(&Compiler) -> R + Se
             let mut lint_store = rustc_lint::new_lint_store(sess.enable_internal_lints());
             if let Some(register_lints) = config.register_lints.as_deref() {
                 register_lints(&sess, &mut lint_store);
-                sess.registered_lints = true;
             }
             sess.lint_store = Some(Lrc::new(lint_store));