R1:be16f9b2cd57

Add a generic "edge.search" method

Summary:
Ref T12337. Ref T5873. This provides a generic "edge.search" method which feels like other "verison 3" `*.search` methods.

The major issues here are:

1. Edges use constants internally, which aren't great for an API.
2. A lot of edges are internal and probably not useful to query.
3. Edges don't have a real "id", so paginating them properly is challenging.

I've solved these things like this:

- Edges must opt-in to being available via Conduit by…