CDP Love: Improve destinations overview

[daniloc]

I don't think the feature preview notice on it is accurate anymore? If it is, we should take this out of feature preview.
We should have screenshots here! It's all so theoretical, and seeing some of this UI requires users to activate an addon they might be unwilling to turn on before knowing it's worthwhile (even for users where their bill is 0, activating add-ons is a friction point)
I'd actually like users to be able to play with this ui, up to and including modifying testing a function, without activating data-pipelines, but that's a heavier lift.
We should mention the filtering stuff - users maybe take it for granted, and maybe don't, but it doesn't hurt to mention
We need to update the limitations - currently we say we only allow 2 fetch calls, but we allow 5.

PostHog/posthog#25566