Use a foreground service for reliable background transmitting

[dshokouhi]

Summary

Hopefully fixes: #3159 by implementing a similar foreground service like in #3369 based on the docs to create a "fake" scanner that looks for nothing to help keep the transmitter alive.

Needs end user testing. 🤞

Screenshots

Link to pull request in Documentation repository

Documentation: home-assistant/companion.home-assistant#pending

Any other notes

Code may not look pretty for now but wanted to get end user feedback

[jpelgrom]

Maybe it's good to split the Bluetooth scan permission into its own PR which we can quickly approve+merge as that fixes an obvious oversight/bug, whereas the foreground service is an effort to improve things but also introduces new behavior?

[dshokouhi]

Maybe it's good to split the Bluetooth scan permission into its own PR which we can quickly approve+merge as that fixes an obvious oversight/bug, whereas the foreground service is an effort to improve things but also introduces new behavior?

actually the scan permission is required in this PR because we are now using the scanner in this sensor where we were not before

[jpelgrom]

I missed that's new, sorry. In that case never mind and let's wait for positive results.

[dshokouhi]

Agreed this requires end users to confirm its working for them as I cannot reproduce