Rollup merge of #105933 - taiki-e:doc-cfg, r=GuillaumeGomez

Add readable rustdoc display for tvOS and watchOS

They are currently displayed as `target_os="..."` in rustdoc, but it would be nice to have readable display like in iOS and other OSs.

<img width="487" alt="cfg" src="https://user-images.githubusercontent.com/43724913/208579395-fd5cf276-8171-47ab-bbed-23e40bb7af11.png">

Author: matthiaskrgr

src/librustdoc/clean/cfg.rs

@@ -507,7 +507,9 @@ impl<'a> fmt::Display for Display<'a> {
                         "openbsd" => "OpenBSD",
                         "redox" => "Redox",
                         "solaris" => "Solaris",
+                        "tvos" => "tvOS",
                         "wasi" => "WASI",
+                        "watchos" => "watchOS",
                         "windows" => "Windows",
                         _ => "",
                     },