Rename SharedUrl to SharedUri (#7084)

This PR renames `SharedUrl` to `SharedUri` to better reflect its intent.

I'm still not entirely happy with this naming, as the file paths that we
can store in here are not _really_ URIs, as they are lacking a protocol.

I want to explore changing `SharedUri` / `SharedUrl` back to alway
storing a URL and treat local filepaths differently, as it seems we're
conflating two different concerns under the same umbrella, at the
moment.

Release Notes:

- N/A

crates/collab_ui/src/notifications/collab_notification.rs

@@ -1,10 +1,10 @@
-use gpui::{img, prelude::*, AnyElement, SharedUrl};
+use gpui::{img, prelude::*, AnyElement, SharedUri};
 use smallvec::SmallVec;
 use ui::prelude::*;
 
 #[derive(IntoElement)]
 pub struct CollabNotification {
-    avatar_uri: SharedUrl,
+    avatar_uri: SharedUri,
     accept_button: Button,
     dismiss_button: Button,
     children: SmallVec<[AnyElement; 2]>,
@@ -12,7 +12,7 @@ pub struct CollabNotification {
 
 impl CollabNotification {
     pub fn new(
-        avatar_uri: impl Into<SharedUrl>,
+        avatar_uri: impl Into<SharedUri>,
         accept_button: Button,
         dismiss_button: Button,
     ) -> Self {