xsrc/60678: WSDISPLAYIO Damage reporting support

["jiaxun.yang%flygoat.com@localhost via gnats" <gnats-admin%NetBSD.org@localhost>]

>Number:         60678
>Category:       xsrc
>Synopsis:       WSDISPLAYIO Damage reporting support
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    xsrc-manager
>State:          open
>Class:          change-request
>Submitter-Id:   net
>Arrival-Date:   Wed Sep 02 14:00:01 +0000 2026
>Originator:     Jiaxun Yang
>Release:        current
>Organization:
>Environment:
>Description:
WSDISPLAY lacks a generic damage reporting mechnisim, and thus display drivers that requires notification for changes on framebuffer content.

Currently, viogpu can't expose dumbfb support due to that, and udlfb is using a very ineffcient way to scan diffs on framebuffer.
>How-To-Repeat:
wsfb X won't work with viogpu driver.
>Fix:
I have a proposal:

https://mail-index.netbsd.org/tech-kern/2025/05/12/msg030435.html

And corresponding implementation:
https://github.com/NetBSD/src/pull/86
https://github.com/NetBSD/xsrc/pull/1