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>

options/locale/locale_en-US.ini

@@ -3152,6 +3152,11 @@ versions.on = on
 versions.view_all = View all
 dependency.id = ID
 dependency.version = Version
+cargo.registry = Setup this registry in the Cargo configuration file (for example <code>~/.cargo/config.toml</code>):
+cargo.install = To install the package using Cargo, run the following command:
+cargo.documentation = For more information on the Cargo registry, see <a target="_blank" rel="noopener noreferrer" href="https://docs.gitea.io/en-us/packages/cargo/">the documentation</a>.
+cargo.details.repository_site = Repository Site
+cargo.details.documentation_site = Documentation Site
 composer.registry = Setup this registry in your <code>~/.composer/config.json</code> file:
 composer.install = To install the package using Composer, run the following command:
 composer.documentation = For more information on the Composer registry, see <a target="_blank" rel="noopener noreferrer" href="https://docs.gitea.io/en-us/packages/composer/">the documentation</a>.
@@ -3228,6 +3233,15 @@ settings.delete.description = Deleting a package is permanent and cannot be undo
 settings.delete.notice = You are about to delete %s (%s). This operation is irreversible, are you sure?
 settings.delete.success = The package has been deleted.
 settings.delete.error = Failed to delete the package.
+owner.settings.cargo.title = Cargo Registry Index
+owner.settings.cargo.initialize = Initialize Index
+owner.settings.cargo.initialize.description = To use the Cargo registry a special index git repository is needed. Here you can (re)create it with the required config.
+owner.settings.cargo.initialize.error = Failed to initialize Cargo index: %v
+owner.settings.cargo.initialize.success = The Cargo index was successfully created.
+owner.settings.cargo.rebuild = Rebuild Index
+owner.settings.cargo.rebuild.description = If the index is out of sync with the cargo packages stored you can rebuild it here.
+owner.settings.cargo.rebuild.error = Failed to rebuild Cargo index: %v
+owner.settings.cargo.rebuild.success = The Cargo index was successfully rebuild.
 owner.settings.cleanuprules.title = Manage Cleanup Rules
 owner.settings.cleanuprules.add = Add Cleanup Rule
 owner.settings.cleanuprules.edit = Edit Cleanup Rule