Rollup merge of #86933 - GuillaumeGomez:cleanup-rustdoc-static-files, r=Manishearth

Clean up rustdoc static files

The `html/static` of rustdoc was starting to be quite a mess... So I moved files in sub-folders to make it easier to follow. Here what remains in `html/static` folder:

```
$ ls
COPYRIGHT.txt  css  fonts  images  js  LICENSE-APACHE.txt  LICENSE-MIT.txt
```

cc ```@jyn514```
r? ```@Manishearth```

Author: JohnTitor

src/bootstrap/test.rs

@@ -742,7 +742,7 @@ impl Step for RustdocTheme {
         let rustdoc = builder.out.join("bootstrap/debug/rustdoc");
         let mut cmd = builder.tool_cmd(Tool::RustdocTheme);
         cmd.arg(rustdoc.to_str().unwrap())
-            .arg(builder.src.join("src/librustdoc/html/static/themes").to_str().unwrap())
+            .arg(builder.src.join("src/librustdoc/html/static/css/themes").to_str().unwrap())
             .env("RUSTC_STAGE", self.compiler.stage.to_string())
             .env("RUSTC_SYSROOT", builder.sysroot(self.compiler))
             .env("RUSTDOC_LIBDIR", builder.sysroot_libdir(self.compiler, self.compiler.host))

src/ci/docker/host-x86_64/mingw-check/Dockerfile

@@ -40,5 +40,5 @@ ENV SCRIPT python3 ../x.py --stage 2 test src/tools/expand-yaml-anchors && \
            /scripts/validate-toolstate.sh && \
            /scripts/validate-error-codes.sh && \
            # Runs checks to ensure that there are no ES5 issues in our JS code.
-           es-check es5 ../src/librustdoc/html/static/*.js && \
-           eslint ../src/librustdoc/html/static/*.js
+           es-check es5 ../src/librustdoc/html/static/js/*.js && \
+           eslint ../src/librustdoc/html/static/js/*.js

src/librustdoc/config.rs

@@ -513,7 +513,7 @@ impl Options {
                     ))
                     .warn("the theme may appear incorrect when loaded")
                     .help(&format!(
-                        "to see what rules are missing, call `rustdoc  --check-theme \"{}\"`",
+                        "to see what rules are missing, call `rustdoc --check-theme \"{}\"`",
                         theme_s
                     ))
                     .emit();