[FEATURE] Add virtual code slots to the virtual lock

[tykeal]

When testing integrations that expect to work with code slots on a lock it would be handy to have the ability to define N number of virtual code slots along with services for setting, getting, and clearing states of them (hopefully with configuration persisting across restarts)

The following services would be helpful to go along with these slots:

• get_user_code -- get the current code defined in a slot
• set_user_code -- set the current code for a slot
• clear_user_code -- disable / unset the current code for a slot

To fully mimic how smart locks operate, the codes should require being unique across all of the slots.