[homekit] Unify all enum handling (#14036)

[homekit] Unify all enum handling (#14036)

* [homekit] unify all enum handling

regardless of if it's a required or optional characteristic,
or even "boolean" enums

then allow number or switch items to be linked with enums

then update the docs listing the numeric value for enums

as part of this, global configuration of thermostat enum values
is no longer supported; you must use metadata.
in particular, for GarageDoorOpener, the global settings didn't
even actually work, so they should work now.

Fixes #13595

* [homekit] default-invert boolean items for garage door states

this was previously handled explicitly by the switch statement.
so need to set the inverted flag now that we're building a
mapping instead

* [homekit] document that CurrentDoorState can be linked to a Contact item
* [homekit] improve docs on invert param to createMapping

also fix a new helper method not properly passing through the inverted
param

Signed-off-by: Cody Cutrer <cody@cutrer.us>