Mobvoi TicWatch GTH (Pro) added as tracker

[DigiH]

Checklist:

• The pull request is done against the latest development branch
• Only one feature/fix was added per PR and the code change compiles without warnings
• I accept the DCO.

[jgbreezer]

Thank you for adding it in the trackers @DigiH . I lost motivation a bit and would have come back to it at some point but was working on other things. Learnt enough during it to make it a bit easier to add something else next time though, which there probably will be in due course. Am going to test this branch.

[DigiH]

@jgbreezer

When trying out the branch with Theengs Gateway please make sure that you're also testing it with a current development branch build of Gateway, as there was an issue with discovering device_tracker without any further properties, like the TicWatch now, which was fixed in the last commit in the development branch.