[Product] Add support for experiments

[joshsny]

Would be nice to be able to create & update simple experiments, and also to get the latest results from them.

[stuartbrameld]

@joshsny jumping ahead here but I was behind PostHog/posthog#36408, this kind of thing longer term would be fantastic e.g 'create a split test between /pricing and /pricing-new and track the change in signup events', or 'get results for the recent pricing page split test'

p.s. unrelated but I'm a little confused between how MaxAI & MCP do/could/should work together in future if could add to any docs around this, thanks

[joshsny]

First PR for adding support for listing experiments thanks to @rodrigoi from the Experiments team