project_panel: Add ability to hide the worktree root

[Angelk90]

Closes #24188

Release Notes:

• Ability to hide main root

Show root	Hide root

[maxdeviant]

How does this behave when you are in a project with multiple worktrees open?

[Angelk90]

@maxdeviant : If there is only one worktree, we respect the hide_root setting, if there is more than one, we force hide_root to false (to show the root of each worktree).

Do you think this could be a solution?

[mikayla-maki]

Thanks for this contribution!

Could you add a test showing this setting functioning?

Also, I think we'll need to make sure that updating this setting will trigger a visible entry recalculation (see relevant code here:

zed/crates/project_panel/src/project_panel.rs

Line 414 in 4453fc4

cx.observe_global::<SettingsStore>(move |this, cx| {

)

Also, could you test how this works with the auto_fold_dirs setting?