CHANGELOG.md: Various entries, mostly xenstore

...grouped by submitters / maintainers

Signed-off-by: George Dunlap <george.dunlap@citrix.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
---
CC: Juergen Gross <jgross@suse.com>
CC: Jan Beulich <jbeulich@suse.com>
CC: Ian Jackson <ian.jackson@citrix.com>

CHANGELOG.md

@@ -26,8 +26,10 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
  - Factored out HVM-specific shadow code, improving code clarity and reducing the size of PV-only hypervisor builds
  - Added XEN_SCRIPT_DIR configuration option to specify location for Xen scripts, rather than hard-coding /etc/xen/scripts
  - xennet: Documented a way for the backend (or toolstack) to specify MTU to the frontend
+ - xenstore can now be live-updated on a running system. (Tech preview)
  - Some additional affordances in various xl subcommands.
  - Added workarounds for the following ARM errata: Cortex A53 #843419, Cortex A55 #1530923, Cortex A72 #853709, Cortex A73 #858921, Cortex A76 #1286807, Neoverse-N1 #1165522
+ - On detecting a host crash, some debug key handlers can automatically triggered to aid in debugging
 
 ### Removed / support downgraded