channel projects (#8456)

Add plumbing for hosted projects. This will currently show them if they
exist
but provides no UX to create/rename/delete them.

Also changed the `ChannelId` type to not auto-cast to u64; this avoids
type
confusion if you have multiple id types.


Release Notes:

- N/A

crates/collab/src/db/tables.rs

@@ -14,6 +14,7 @@ pub mod extension;
 pub mod extension_version;
 pub mod feature_flag;
 pub mod follower;
+pub mod hosted_project;
 pub mod language_server;
 pub mod notification;
 pub mod notification_kind;