modbus reliability and throtling changes

[pmp02]

• force close the sockets of the API calls to prevent keep alive and put too much pressure on the IAM module
• split the API call in two calls with different timings (the input registers at 10secs or lower and the configuration registers at 300 seconds - as these don't change that often).
• I also added the Off ventilator status, so I can better monitor the behavior of the unit.
• handling the MB_DISCONNECT and ERROR statuses from the unit, use "temporary unavailable" and back-off API requests exponentially until the unit is available again
• Added several tweaking options in UI directly. These can be used to tune the load on the IAM module.
  • max_registers_per_api_request
  • web_api_inter_chunk_delay_ms
  • status_poll_interval_ms
  • config_poll_interval_ms
  • status_off_skip_factor: skip api requests N-1 times when the ventilators are off

[pmp02]

Hi @AN3Orik !
When you get the chance, the latest push (commit ad4c2fa) should pass all workflows.
Thank you!

[AN3Orik]

Thanks for pull request, but it's too complicated to merge without break something.
I ported your Fan off feature to latest version (https://github.com/AN3Orik/systemair/releases/tag/v1.0.19)
For more info about hanging fix look at changelog.