Wait for capabilities message from Xorg

[matt335672]

This is partly mentioned in #1816

This commit adds a stage into the Xorg connection status to wait for the capabilities message from the Xorg server.

This allows us to move the xorgxrdp version check to xrdp from the X server for better reporting to the user.

This PR needs neutrinolabs/xorgxrdp#332 to function correctly, but can be merged separately.

Currently, if the xrdp and xorgxrdp versions don't match:-

1. The connection terminates immediately.
2. The version mismatch is reported in ~/.xorgxrdp.$D.log (not xrdp.log)
3. The X server aborts.

With both of these PRs:-

1. An error is displayed to the user
2. The version mismatch is reported in xrdp.log
3. The X server continues to run.

Screenshot for a version mismatch:-

Corresponding xrdp.log:-

[2024-08-06T11:32:08.469+0100] [INFO ] [lib_mod_connect(xup.c:269)] lib_mod_connect: connecting via UNIX socket
[2024-08-06T11:32:08.469+0100] [INFO ] [lib_mod_connect(xup.c:304)] lib_mod_connect: connected to Xserver (Xorg) sck 29
[2024-08-06T11:32:08.469+0100] [INFO ] [lib_mod_log_peer(xup.c:79)] lib_mod_log_peer: xrdp_pid=80398 connected to Xorg_pid=80518 Xorg_uid=1001 Xorg_gid=1001 client=[::ffff:172.19.73.10]:32884
[2024-08-06T11:32:08.476+0100] [ERROR] [lib_mod_process_message(xup.c:1839)] Xorg module has version 20240806, expected 20240805
[2024-08-06T11:32:08.479+0100] [ERROR] [xrdp_wm_log_msg(xrdp_wm.c:2434)] xrdp_wm_log_msg: Error connecting to user session

[metalefty]

I like the idea.

[metalefty]

@matt335672 Let's merge this if this doesn't interrupt what we are working on now.

[matt335672]

Thanks - I'll rebase and retest first.

[matt335672]

One small change - I've displayed the version number mismatch for the user:-

This should help users triage problems introduced by distros, as an internet search may reveal the issue.