add heatpump pool on/off, pool active, MP100 shunt setpoint and pool pump

Tested with a heatpump (0x08) and MP100 pool module (0x11), custom entities
compared against RC300 operation and a power meter on the circulation pump.

- boiler `poolon` (0x48A offset 0), writable, RC300 writes 01/00
- boiler `hppoolon` (0x488 offset 0 bit 6), pool heating actually active
- pool `poolshuntset` (0x5C4 offset 0, heatpump -> MP100), shunt setpoint;
  `poolshunt` follows within ~2 min
- pool `poolpump` (0x5BA offset 4), 0 = running, 2 = off. This byte is only
  in MP100 -> heatpump telegrams, so the pool module now also handles
  telegrams it sends to other devices
- simulator: `test pool`

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013YrkDbvxEv3ZMS7SPSKCGd

CHANGELOG_LATEST.md

@@ -19,6 +19,7 @@ This release is based on the latest Espressif/Arduino core version 3. It brings
 - `show system` reports the Ethernet status on boards with a PHY, so a failed initialisation or a link that never came up is visible instead of Ethernet being omitted completely. Also shows the loop task's lowest free stack, to help diagnose reboots
 - new Application Setting "Automatically check for firmware updates", off by default. When enabled EMS-ESP asks emsesp.org for the latest version once a day on its own, otherwise it only asks when the WebUI wants to show it, so an unattended system never contacts emsesp.org
 - Automatically check and convert older 3.8.x filesystem to the new 3.9.0 format
+- heatpump pool: `poolon` (switch, 0x48A), `hppoolon` (pool heating active, 0x488), MP100 `poolshuntset` (0x5C4) and `poolpump` (0x5BA)
 
 ## Fixed