api: add ConnectionPoolSettings into ProxyProtocolUpstreamTransport (#…

…37177)

Commit Message:
Add `ConnectionPoolSettings` in proxy_protocol upstream transport
socket.
It customizes the behavior of connection pool.

Additional Description:
Risk Level: LOW
Testing: CI
Docs Changes:
Release Notes:
Platform Specific Features:
[Optional Runtime guard:]
Fixes #37126
[Optional Fixes commit #PR or SHA]
[Optional Deprecated:]
[Optional [API
Considerations](https://github.com/envoyproxy/envoy/blob/main/api/review_checklist.md):]

---------

Signed-off-by: Yuchen Dai <[email protected]>

api/envoy/extensions/transport_sockets/proxy_protocol/v3/upstream_proxy_protocol.proto

@@ -24,4 +24,13 @@ message ProxyProtocolUpstreamTransport {
 
   // The underlying transport socket being wrapped.
   config.core.v3.TransportSocket transport_socket = 2 [(validate.rules).message = {required: true}];
+
+  // If this is set to true, the null addresses are allowed in the PROXY protocol header.
+  // The proxy protocol header encodes the null addresses to AF_UNSPEC.
+  // [#not-implemented-hide:]
+  bool allow_unspecified_address = 3;
+
+  // If true, all the TLVs are encoded in the connection pool key.
+  // [#not-implemented-hide:]
+  bool tlv_as_pool_key = 4;
 }