companion: get/set timezone offset for clock

* Add tz_offset companion prefs and get/set commands for companion cli
* Use tz_offset for clock on display

Signed-off-by: Aleksei Mamlin <mamlinav@gmail.com>

variants/thinknode_m8/platformio.ini

@@ -22,7 +22,6 @@ build_flags = ${nrf52_base.build_flags}
   -D UI_HAS_ROTARY_INPUT=1
   -D UI_HAS_NAV_INPUT=1
   -D UI_RECENT_LIST_SIZE=9
-  -D UI_TZ_OFFSET=-4 # GMT-4
   -D UI_MSG_PREVIEW_SIZE=165
   -D EINK_MAX_PARTIAL_REFRESH=60
   -D EINK_DISPLAY_MODEL=GxEPD2_154_D67