Screen sharing is erratic under Wayland when switching between sharing modes

[Nathan Teodosio]

In Wayland,
open Chromium,
go to https://mozilla.github.io/webrtc-landing/gum_test.html,
Screen Capture,
click the "Window" tab of the dialog,
choose any window in the pop-up window and click "Share", but don't click the other "Share" in the transient dialog inside Chromium.

Then, change your mind,
click the "Entire screen" tab,
choose any display in the pop-up window and click "Share".

Expected
--------

The display is shared immediately.

Observed
--------

This appears in the stderr:

--->
[E][02607.112169][module-protocol-: 609 lock_socket()] server 0x1fec07ecef80: unable to lock lockfile '/run/user/1000/snap.chromium/pipewire-0.lock': Resource temporarily unavailable (maybe another daemon is running)
[E][02607.112301][ conf.c: 332 load_module()] config 0x1fec07fd8000: could not load mandatory module "libpipewire-module-protocol-native": Resource temporarily unavailable
[52486:52486:0524/082713.056397:ERROR:shared_screencast_stream.cc(426)] Failed to create PipeWire context
[52486:52486:0524/082713.056420:ERROR:base_capturer_pipewire.cc(81)] ScreenCastPortal failed: 1
<---

and the display takes a considerably long time — about 10 s — to be shared, which is unnacceptable on its own, but also this time is also sufficient to lead the user to think: "it doesn't and won't work, let me just cancel this."

Extra
-----

Sometimes the pop-up window is also displayed twice, and sometimes the first one has no effect. Similar to reports in LP:1849478.