testing tools for extauth/rbac/etc policies

Inspired by https://twitter.com/fuzzyKB/status/1304180270858338309.

I think much like the route test tool, it would be useful to have some tools that can more easily test matching/rbac/extauth/jwt/etc. policies.

This would allow us to more easily write expectation style testing for different policies without having to stand up a full proxy and perform integration testing.

I'm imagining the ability to provide different configurations, and then provide input requests/JWT/etc. and potentially even specify different extauth responses to drive test cases. Under the hood this would use all of the prod code that actually performs these operations, extracted from the owning filters and network infra.