add waypoint context to envoyfilter

[dprotaso]

Part of istio/istio#43720

/assign @howardjohn

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[howardjohn]

If we are to implement EnvoyFilter on waypoint I definitely think this is a step in the right direction. However, I don't think we yet have consensus that it is something that is desired at all. We probably would need to settle that before moving forward

[keithmattix]

I added my thoughts here: istio/istio#55149 (comment)

[linsun]

We discussed this in a meeting recently, and we couldn't reach consensus that we need to implement envoy filter support in waypoint.

[zirain]

IMO, you cannot add every features envoy supported into first class API.

For RateLimit, ExtProc, we can support it by first class API. How to tweak some configuration in Cluster/Route/Listerner?

If you search the github issue, lot of edge cases were fixed by EnvoyFilter, I don't think it won't happen in Waypoint.

In the end, every vendor need to add EF support in their forks, that's the worst to the community.