Add missing states to alarm_control_panel entity

[DeathCamel58]

It looks like alarm_control_panel is missing a couple states in VALID_STATES. The states that seem to be missing are:

    STATE_ALARM_PENDING,
    STATE_ALARM_ARMING,
    STATE_ALARM_DISARMING,

I'd like these three states to be included to allow the Prometheus integration to export all possible states of an alarm_control_panel.

[MartinHjelmare]

Valid states is in this case used for reproducing the state. That means there needs to be a corresponding service. The mentioned states don't have a corresponding service and are not meant to have that.

Why does Prometheus need to change the reproduce state module of the alarm control panel to export the alarm control panel state?

[DeathCamel58]

Prometheus queries the attributes of a climate, humidifier, and fan device to get a list of modes supported, and exports a metric for each mode. However, there doesn't seem to be an equivalent for an alarm_control_panel, and I'm working on adding that support.

Maybe instead we could add a way to query which modes are supported for alarm_control_panels in a similar way instead?

[MartinHjelmare]

Nowadays entity integrations with a defined set of string states use a StrEnum to describe this. Look at eg the lawn mover integration. The alarm control panel should probably be migrated to something similar.

This is a bit more involved change than simply adding the enum though as requiring its usage is a breaking change for existing integrations. A new property should probably be introduced at the same time, that returns the enum, and is used by the state property. Not implementing the new property could generate a warning during a deprecation period.