clock: Cleanup ReplicaId, Lamport and Global (#40600)

- Notable change is the use of a newtype for `ReplicaId`
- Fixes `WorktreeStore::create_remote_worktree` creating a remote
worktree with the local replica id, though this is not currently used
- Fixes observing the `Agent` (that is following the agent) causing
global clocks to allocate 65535 elements
- Shrinks the size of `Global` a bit. In a local or non-collab remote
session it won't ever allocate still.

Release Notes:

- N/A *or* Added/Fixed/Improved ...

crates/multi_buffer/src/multi_buffer.rs

@@ -666,7 +666,7 @@ impl MultiBuffer {
             paths_by_excerpt: Default::default(),
             buffer_changed_since_sync: Default::default(),
             history: History {
-                next_transaction_id: clock::Lamport::default(),
+                next_transaction_id: clock::Lamport::MIN,
                 undo_stack: Vec::new(),
                 redo_stack: Vec::new(),
                 transaction_depth: 0,