project panel: Allow selecting multiple entries & add support for multiselect actions (#12363)

Fixes #4983 
TODO:
- [x] Improve release note.
- [x] Tests

Release Notes:

- Project panel now supports selecting multiple entries via cmd-click
and shift-click/shift-up/shift-down.
- Added support for handling multiple selected project panel entries to
Cut, Copy, Trash and Delete actions.

crates/worktree/src/worktree.rs

@@ -5113,6 +5113,7 @@ pub struct ProjectEntryId(usize);
 
 impl ProjectEntryId {
     pub const MAX: Self = Self(usize::MAX);
+    pub const MIN: Self = Self(usize::MIN);
 
     pub fn new(counter: &AtomicUsize) -> Self {
         Self(counter.fetch_add(1, SeqCst))