Allow to customize the notifications position

[EDM115]

What are you proposing?

Currently (ex when an agent requires interaction from the user and Zed isn't focused), we receive notifications.
We can already select on which display (zed://settings/agent.notify_when_agent_waiting) but the notification will always be on the top right of the screen.
Users might want to chose another corner of the monitor to display said notifications (ex bottom right).

Why does this matter?

Users might want their notifications to follow other apps conventions. Furthermore, this part of the screen might already be occupied by something else.

Are there any examples or context?

None

Possible approach

What seems to control this is this line (top_right()) :

zed/crates/agent_ui/src/ui/agent_notification.rs

Lines 41 to 48 in 715cd42

	let bounds = gpui::Bounds::<Pixels> {
	origin: screen.bounds().top_right()
	- point(
	size.width + notification_margin_width,
	notification_margin_height,
	),
	size,
	};

This itself seems to be defined here : crates/gpui/src/geometry.rs.
There seems to be lots of methods that already implement other screen corners and even centered (which could be cool to have the notification be at the bottom center for ex, easier to notice and doesn't move the focus away from where we're usually looking at).
For the setting itself, I believe it shouldn't be in the Agent category as other parts of Zed might wanna use notifications in the future. Window & Layout -> Window seems more fitting.