Add Cargo package registry (#21888)

This PR implements a [Cargo registry](https://doc.rust-lang.org/cargo/)
to manage Rust packages. This package type was a little bit more
complicated because Cargo needs an additional Git repository to store
its package index.

Screenshots:

![grafik](https://user-images.githubusercontent.com/1666336/203102004-08d812ac-c066-4969-9bda-2fed818554eb.png)

![grafik](https://user-images.githubusercontent.com/1666336/203102141-d9970f14-dca6-4174-b17a-50ba1bd79087.png)

![grafik](https://user-images.githubusercontent.com/1666336/203102244-dc05743b-78b6-4d97-998e-ef76341a978f.png)

---------

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

templates/user/settings/packages.tmpl

@@ -4,6 +4,7 @@
 	<div class="ui container">
 		{{template "base/alert" .}}
 		{{template "package/shared/cleanup_rules/list" .}}
+		{{template "package/shared/cargo" .}}
 	</div>
 </div>
 {{template "base/footer" .}}