Convert tidy to a non-egg Python package

It seems that servo-tidy is only used by webrender in my GitHub
searches. WebRender could simply use `rustfmt` and the tidy on pypi
hasn't been updated since 2018. Converting tidy to a normal Python
package removes the maintenance burden of continually fixing the easy
install configuration.

Fixes #29094.
Fixes #29334.

python/tidy/tests/speclink.rs

@@ -0,0 +1,32 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+impl SpecLinkMethods for SpecLink {
+    amacro!("Macros inside impls should trigger spec checks.")
+
+    // Method declarations should trigger spec checks.
+    fn Test(&self) -> f32 {
+        amacro!("Macros inside function declarations should not trigger spec checks.");
+        if unsafe { false } {
+        }
+        amacro!("Even if there's weird brace counts.");
+        0
+    }
+
+    // A spec link.
+    // https://example.com/
+    fn Foo() {}
+
+    /// A spec link.
+    /// <https://example.com/>
+    fn Foo() {}
+
+    /// A spec link.
+    /// <https://example.com/>
+    /// Doc comments are OK
+    // Regular comments are OK
+    #[allow(attributes_too)]
+    fn Foo() {}
+}
+