Do more on channel join (#7268)

This change makes it so that if you are the first to join a channel,
your project is automatically shared.

It also makes it so that if you join a channel via a link and there are
no shared projects, you open the notes instead of an empty workspace
with nothing.

This is to try and address the discoverability of project sharing: we've
had
two reviews that have talked about channels, but not talked about
sharing
projects into them, which makes me suspect they didn't know about the
feature.

Release Notes:

- Added a setting `share_on_join` (defaulting to true). When set, and
you join an empty channel, your project is automatically shared.

crates/call/src/call_settings.rs

@@ -7,6 +7,7 @@ use settings::Settings;
 #[derive(Deserialize, Debug)]
 pub struct CallSettings {
     pub mute_on_join: bool,
+    pub share_on_join: bool,
 }
 
 /// Configuration of voice calls in Zed.
@@ -16,6 +17,11 @@ pub struct CallSettingsContent {
     ///
     /// Default: false
     pub mute_on_join: Option<bool>,
+
+    /// Whether your current project should be shared when joining an empty channel.
+    ///
+    /// Default: true
+    pub share_on_join: Option<bool>,
 }
 
 impl Settings for CallSettings {