debugger: Add Debug Panel context menu (#28847)

This PR adds a debug panel context menu that will allow a user to select
which debug session items are visible.

The context menu will add to the pane that was right clicked on.

<img width="1275" alt="Screenshot 2025-04-16 at 2 43 36 AM"
src="https://github.com/user-attachments/assets/330322ff-69db-4731-bbaf-3544d53f2f15"
/>


Release Notes:

- N/A

crates/debugger_ui/src/session/running/loaded_source_list.rs

@@ -3,7 +3,7 @@ use project::debugger::session::{Session, SessionEvent};
 use ui::prelude::*;
 use util::maybe;
 
-pub struct LoadedSourceList {
+pub(crate) struct LoadedSourceList {
     list: ListState,
     invalidate: bool,
     focus_handle: FocusHandle,

crates/debugger_ui/src/session/running/variable_list.rs

@@ -194,6 +194,10 @@ impl VariableList {
         }
     }
 
+    pub(super) fn has_open_context_menu(&self) -> bool {
+        self.open_context_menu.is_some()
+    }
+
     fn build_entries(&mut self, cx: &mut Context<Self>) {
         let Some(stack_frame_id) = self.selected_stack_frame_id else {
             return;