Add wind_speed and visibility units to weather components

[PhracturedBlue]

Description:

Adds units for wind_speed and visibility to weather components. Adds new 'speed' unit to valid units. Add conversions from metric to imperial units for speed
This change was requested in: #11136

Checklist:

If the code communicates with devices, web services, or third-party tools:

• Local tests with tox run successfully. Your PR cannot be merged unless tests pass

If the code does not interact with devices:

• Local tests with tox run successfully. Your PR cannot be merged unless tests pass
• Tests have been added to verify that the new code works.

[pvizeli]

@fabaff can you look at this?

[fabaff]

I don't like the idea that we start to implement our own way to convert unit of measurements. This smells like reinventing the wheel. Instead we should start to use pint or a similar library to do it. It doesn't stop with wind speed there are a lot of other unit of measurements which we need to convert one day.

[PhracturedBlue]

How do you want me to proceed? Using a new library to convert units seems like a large architectural change. I think that is beyond the scope of this feature, and I see no realistic way that I can guess how you'd like it architected. The Ecobee weather component is pretty broken right now and needs a fix, be it the simpler version (#11136) or this one..

[pvizeli]

Looks dead