Add server side events to Smlight integration

[tl-sl]

Breaking change

Proposed change

Add server side events (SSE) client to Smlight integration and hook them up for switches platform. SSE events will also be used for update entities and a couple of other sensors later.

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• Breaking change (fix/feature causing existing functionality to break)
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• This PR fixes or closes issue: fixes #
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[joostlek]

Should the integration type be changed to local_push?

[tl-sl]

no, the majority of sensors are still polled. Events are mainly only available for settings changes and updates.

[joostlek]

We categorize them with the best way they can do it

[tl-sl]

well in that case I suppose it should be changed then