arti-client: Make dirmgr() and circmgr() return &Arc<..>

Previously they returned an Arc, which wasn't necessary unless the
client actually _wanted_ a new Arc.

This would be an API break, except that these functions are marked
'experimental-api', so semver does not apply; nonetheless I've noted
the break in semver_status.md, just in case we care.

Closes #369

crates/arti-client/src/client.rs

@@ -783,8 +783,8 @@ impl<R: Runtime> TorClient<R> {
     /// This function is unstable. It is only enabled if the crate was
     /// built with the `experimental-api` feature.
     #[cfg(feature = "experimental-api")]
-    pub fn dirmgr(&self) -> Arc<dyn tor_dirmgr::DirProvider + Send + Sync> {
-        Arc::clone(&self.dirmgr)
+    pub fn dirmgr(&self) -> &Arc<dyn tor_dirmgr::DirProvider + Send + Sync> {
+        &self.dirmgr
     }
 
     /// Return a reference to this this client's circuit manager.
@@ -792,8 +792,8 @@ impl<R: Runtime> TorClient<R> {
     /// This function is unstable. It is only enabled if the crate was
     /// built with the `experimental-api` feature.
     #[cfg(feature = "experimental-api")]
-    pub fn circmgr(&self) -> Arc<tor_circmgr::CircMgr<R>> {
-        Arc::clone(&self.circmgr)
+    pub fn circmgr(&self) -> &Arc<tor_circmgr::CircMgr<R>> {
+        &self.circmgr
     }
 
     /// Return a reference to the runtime being used by this client.

doc/semver_status.md

@@ -17,4 +17,11 @@ Don't document other changes in this file.
 We can delete older sections here after we bump the releases.
 
 
-## Since Arti 0.0.3
+## Since Arti 0.1.0
+
+arti-client:
+
+  api-break (experimental only): changed circmgr() and dirmgr() to return
+  &Arc, not Arc.
+
+