linux: Tweak file chooser dialogs (#14526)

Mostly some small tweaks to the file chooser dialogs.

Fixes https://github.com/zed-industries/zed/issues/14127 (along with the
`ashpd` update in https://github.com/zed-industries/zed/pull/14401)

Also included a fix
(https://github.com/zed-industries/zed/commit/971d67c994dd595454cc4bc92bdf33d9da30a31a)
for an issue that made multiple file chooser dialogs pop up on Wayland
when doing CTRL + O and quickly pressing the escape key.

Release Notes:

- N/A