Some updates to the UI specific issue template.
The previous 'Old UI or New UI' question is no longer relevant and considering the amount of visual change we've had, this leads to folks answering things like 'Consul 1.10.0+ent with new, new UI'. Now it's just "The Consul UI".
I mainly took the rest from the current Consul Core issue template but made it relevant to the UI both for issues/bugfixes and for suggestions/improvements.
