Rollup merge of rust-lang#90354 - xFrednet:00000-lets-deploy-clippy-docs, r=Mark-Simulacrum

Document clippy on nightly-rustc

Adding Clippy's docs to nightly-rustc, based on commit 01cf0bd. This PR only adds `clippy_utils` to the documentation. I've decided to only document one crate for now, as `clippy_lints` etc. contain very specific and undocumented functions which aren't really reusable. I'm guessing that they would mostly clutter up the search results with little benefit.

`./x.py --stage 1 doc src/tools/clippy` if working fine now after the help that ```@jyn514``` and ```@ehuss``` have provided. A big THANK YOU to them!

Author: matthiaskrgr

src/bootstrap/builder.rs

@@ -482,6 +482,7 @@ impl<'a> Builder<'a> {
                 doc::RustByExample,
                 doc::RustcBook,
                 doc::CargoBook,
+                doc::Clippy,
                 doc::EmbeddedBook,
                 doc::EditionGuide,
             ),

src/bootstrap/doc.rs

@@ -755,6 +755,7 @@ tool_doc!(
     "src/tools/rustfmt",
     ["rustfmt-nightly", "rustfmt-config_proc_macro"],
 );
+tool_doc!(Clippy, "clippy", "src/tools/clippy", ["clippy_utils"]);
 
 #[derive(Ord, PartialOrd, Debug, Copy, Clone, Hash, PartialEq, Eq)]
 pub struct ErrorIndex {