Remove support for compiler plugins.

They've been deprecated for four years.

This commit includes the following changes.
- It eliminates the `rustc_plugin_impl` crate.
- It changes the language used for lints in
  `compiler/rustc_driver_impl/src/lib.rs` and
  `compiler/rustc_lint/src/context.rs`. External lints are now called
  "loaded" lints, rather than "plugins" to avoid confusion with the old
  plugins. This only has a tiny effect on the output of `-W help`.
- E0457 and E0498 are no longer used.
- E0463 is narrowed, now only relating to unfound crates, not plugins.
- The `plugin` feature was moved from "active" to "removed".
- It removes the entire plugins chapter from the unstable book.
- It removes quite a few tests, mostly all of those in
  `tests/ui-fulldeps/plugin/`.

Closes #29597.

compiler/rustc_interface/src/queries.rs

@@ -148,12 +148,8 @@ impl<'tcx> Queries<'tcx> {
             );
             let dep_graph = setup_dep_graph(sess, crate_name, stable_crate_id)?;
 
-            let lint_store = Lrc::new(passes::create_lint_store(
-                sess,
-                &*self.codegen_backend().metadata_loader(),
-                self.compiler.register_lints.as_deref(),
-                &pre_configured_attrs,
-            ));
+            let lint_store =
+                Lrc::new(passes::create_lint_store(sess, self.compiler.register_lints.as_deref()));
             let cstore = FreezeLock::new(Box::new(CStore::new(
                 self.codegen_backend().metadata_loader(),
                 stable_crate_id,