egl: reenable partial redraw with a warning when using gallium hud

egl: reenable partial redraw with a warning when using gallium hud

Partial revert of e516a0a94f ("egl: disable partial redraw when gallium
hud is active").

We shouldn't change the behavior of the application when the hud is
enabled, doing so could make it harder do diagnose issues. Instead, now
we warn and ask the user to manually disable the extension if he
considers it to be worth it.

Fixes: e516a0a94f ("egl: disable partial redraw when gallium hud is active")
Signed-off-by: Italo Nicola <italonicola@collabora.com>
Reviewed-by: Eric Engestrom <eric@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/23456>