Add a registry for GitHostingProviders (#11470)

This PR adds a registry for `GitHostingProvider`s.

The intent here is to help decouple these provider-specific concerns
from the lower-level `git` crate.

Similar to languages, the Git hosting providers live in the new
`git_hosting_providers` crate.

This work also lays the foundation for if we wanted to allow defining a
`GitHostingProvider` from within an extension. This could be useful if
we wanted to extend the support to work with self-hosted Git providers
(like GitHub Enterprise).

I also took the opportunity to move some of the provider-specific code
out of the `util` crate, since it had leaked into there.

Release Notes:

- N/A

crates/git/src/repository.rs

@@ -1,4 +1,5 @@
 use crate::blame::Blame;
+use crate::GitHostingProviderRegistry;
 use anyhow::{Context, Result};
 use collections::HashMap;
 use git2::{BranchType, StatusShow};
@@ -71,13 +72,19 @@ impl std::fmt::Debug for dyn GitRepository {
 pub struct RealGitRepository {
     pub repository: LibGitRepository,
     pub git_binary_path: PathBuf,
+    hosting_provider_registry: Arc<GitHostingProviderRegistry>,
 }
 
 impl RealGitRepository {
-    pub fn new(repository: LibGitRepository, git_binary_path: Option<PathBuf>) -> Self {
+    pub fn new(
+        repository: LibGitRepository,
+        git_binary_path: Option<PathBuf>,
+        hosting_provider_registry: Arc<GitHostingProviderRegistry>,
+    ) -> Self {
         Self {
             repository,
             git_binary_path: git_binary_path.unwrap_or_else(|| PathBuf::from("git")),
+            hosting_provider_registry,
         }
     }
 }
@@ -246,6 +253,7 @@ impl GitRepository for RealGitRepository {
             path,
             &content,
             remote_url,
+            self.hosting_provider_registry.clone(),
         )
     }
 }