improve quickstart guide UX

[nirrozenbaum]

as of today, our quickstart guides have several steps where one should select a tab for gateway provider.
this selection has to be done in multiple steps, which gives a non-intuitive UX.
ideally, we should be able to select gateway provider once (e.g., kgateway/istio/etc) and get an quickstart guides that can be followed that matches this selection.

from a discussion in one of the recent community calls, @mikemorris mentioned this is possible.

[nirrozenbaum]

@mikemorris do you have capacity to have a look on this?