[water_heater] (1/4) Implement API/Core/component for new water_heater component (#12498)

Co-authored-by: pre-commit-ci-lite[bot] <117423508+pre-commit-ci-lite[bot]@users.noreply.github.com>
Co-authored-by: J. Nick Koston <nick+github@koston.org>
Co-authored-by: J. Nick Koston <nick@home-assistant.io>
Co-authored-by: J. Nick Koston <nick@koston.org>

CODEOWNERS

@@ -537,6 +537,7 @@ esphome/components/version/* @esphome/core
 esphome/components/voice_assistant/* @jesserockz @kahrendt
 esphome/components/wake_on_lan/* @clydebarrow @willwill2will54
 esphome/components/watchdog/* @oarcher
+esphome/components/water_heater/* @dhoeben
 esphome/components/waveshare_epaper/* @clydebarrow
 esphome/components/web_server/ota/* @esphome/core
 esphome/components/web_server_base/* @esphome/core