Screen-brightness-control

* Fix `filter_monitors` not correctly raising `LookupError` when no monitors were found
* Fix tests for `helpers._monitor_brand_lookup`

* Fix filtering by index in `filter_monitors`
* Add `check_output` helper function to `helpers.py` for calling commands.
* Caching tweaks

* Logarithmic brightness scaling in `fade_brightness`
* Sped up `linux.XRandr.get_display_info`
* Improve `linux.SysFiles` and `linux.Light` display compatibility
* Retry DDCUtil commands up to 10 times (18)
* Allow `filter_monitors` up to 3 retries (18)
* Remove deprecated `EDID.parse_edid` method
* Remove deprecated `linux.XBacklight` class
* Deprecated `linux.XRandr.get_display_interfaces`

* Fix DDCUtil brightness units out of range (17)
* Fix I2C brightness units out of range

* Fix display information being overridden by `None` values

Added/Changed
* Added native desktop monitor control for Linux via `linux.I2C` class
* Add `get_methods` function
* Add `EDID.parse` method with massively improved EDID parsing capabilities
* Move generic, independent functions into `helpers.py`
* Remove some useless caching
Deprecated for removal in next release
* Deprecated `EDID.parse_edid` method
* Deprecated `linux.XBacklight` class (see [c9f798b](https://github.com/Crozzers/screen_brightness_control/commit/c9f798b54a1159f680d1759e363657ef7245ed2d) for reasoning)