Add support for delayed actions

[ldotlopez]

Checklist

• I checked for similar existing requests (both open and closed) before posting.
• My request is generic, other users may benefit from it too.

Proposal

Add support for delayed actions like: turn on the A/C in 2 hours

This is different that scheduling with a calendar or fixed hours, sometimes I need to turn on / off some device after some interval.

I'm about to take a look at the code and do this myself, but before going into depth I want to know if there is interest in this feature and if it may be merged

Additional info

I tried to implement it using standard timers, helpers, automations and scripts but it gets to messy, fragile, complicated and not reusable, not to mention the UI.

I think that scheleduler-component has all the infrastructure ready to support this feature: code and UI components.

• Action should be disabled after finish due to it's nature, reenabling it should start the timer again
• Disabling the action causes the internal timer to be canceled.

[github-actions]

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