Unify the tasks modal and the new session modal (#31646)

Release Notes:

- Debugger Beta: added a button to the quick action bar to start a debug
session or spawn a task, depending on which of these actions was taken
most recently.
- Debugger Beta: incorporated the tasks modal into the new session modal
as an additional tab.

---------

Co-authored-by: Julia Ryan <juliaryan3.14@gmail.com>
Co-authored-by: Julia Ryan <p1n3appl3@users.noreply.github.com>
Co-authored-by: Anthony Eid <hello@anthonyeid.me>
Co-authored-by: Mikayla <mikayla@zed.dev>

crates/gpui/src/key_dispatch.rs

@@ -27,7 +27,7 @@
 ///
 /// The keybindings themselves are managed independently by calling cx.bind_keys().
 /// (Though mostly when developing Zed itself, you just need to add a new line to
-///  assets/keymaps/default.json).
+///  assets/keymaps/default-{platform}.json).
 ///
 /// ```rust
 /// cx.bind_keys([