added remove_device function to BleakClient interface and implement it for WinRT backend

[jochenjagers]

Hello,

this PR adds a remove_device function to be able to remove a device without the need of connecting to it before.
This was inspired by the remove_device function for the bluez backend from another pull request (https://github.com/hbldh/bleak/pull/640/files#diff-dca4aa1d374b221291b543a5d1296bbf912b43d1e2ebc51ed11c1eb153fbb89bR118)
As I have no possibility to test with the bluez backend at the moment I did not copy it from there.

Additionally I moved the validate_address function out of the bluez backend utils into a generic utils file to be able to use it in the WinRT backend as well.

[dlech]

EDIT: disregard this comment, I had disconnection on my mind instead of removing pairing info

Thanks for the PR. However, BlueZ is the only backend that has a problem with not disconnecting sometimes and it is not possible to "disconnect" in any other backend without "connecting" first. Something similar was recently discussed in #992. Perhaps the feature that was added to close that issue could be of help for your use case (it allows "connecting" in the BlueZ backend without disconnecting first)?

[dlech]

Can we not just make sure that calling the existing unpair() method works without being connected instead of adding a new method?

[dlech]

Related issue: #309

[jochenjagers]

Changing the unpair() function was also my first idea and I did this in the version of bleak I am currently using on my own.
But I was not happy about the complexity which was added to unpair() by this. And it might not be clear to the user that pair() needs a connection but unpair() can be used without. It is obvious if you know how it works but it might be confusing if you are new to the topic.
But I will have a look on unpair() again and check for an easy solution.

[jochenjagers]

What do you think about this solution?
develop...jochenjagers:bleak:feature/winrt-unpair-without-connect
It allows unpair without connection for the WinRT backend without adding a new function to the inferface.

[dlech]

It will be easier to make specific comments in a pull request, but in general, it looks like the right approach.