Envoy should be able to describe (Wasm) ABIs it supports

Title: Envoy should be able to describe (Wasm) ABIs it supports

Context:

• consider a use case of a marketplace with Wasm extensions for Envoy
• from a user perspective, it's important to know whether a given extension is supported by a particular Envoy distribution he is using right now
• the assumption is that an answer like "use Envoy vX.Y.Z+" is not good enough (a user might be using either a 3rd party closed source Envoy distro, or a nightly build of upstream Envoy, etc)

Proposal:

• Add to Envoy the ability to describe (Wasm) ABIs it supports
• The initial focus is on the offline scenario where it is a user, or a marketplace, or a vendor, who needs to know this info
• The online scenario, where it is a Control Plane who needs to know this info, is currently out of scope

Example use cases:

• a user runs envoy --list-abis to get the precise list of (Wasm) ABIs this particular Envoy distro supports, e.g.

  envoy:
    version:
     ... 
    abis:
      v1:
        host:
          network_filter:
            ...
          http_filter:
            ...
          access_log:
            ...
          http_client:
            proxy_http_call:   SUPPORTED
          grpc_client:
            proxy_grpc_call:   SUPPORTED
            proxy_grpc_stream: SUPPORTED
            proxy_grpc_send:   SUPPORTED
          tcp_client:
            ...
          udp_client:
            ...
        ...
        extension:
          network_filter:
            ...
          http_filter:
            ...
          access_log:
            ...
          http_client:
            proxy_on_http_call_response:           SUPPORTED
          grpc_client:
            proxy_on_grpc_create_initial_metadata: SUPPORTED
            proxy_on_grpc_receive:                 DEPRECATED
          tcp_client:
            ...
          udp_client:
            ...
        ...
  

• a user then comes to a marketplace site, provides info from above and gets back the exact info on what extensions (and their versions) are applicable to him
• a marketplace runs envoy --list-abis on popular Envoy distributions (e.g. upstream, getenvoy, istio, solo, etc) to provide compatibility info in advance
• a vendor of a closed source Envoy distribution runs envoy --list-abis on his own binaries and submits this info to a marketplace in order to be present in the compatibility matrix for each extension in the catalog