Combine H1 and H2 conn_pool implementations (#9668)

Signed-off-by: Greg Greenway <ggreenway@apple.com>

Mirrored from https://github.com/envoyproxy/envoy @ be8d4caf3701e07f338cf1a53657451d4bcd440b

envoy/api/v2/core/protocol.proto

@@ -117,6 +117,10 @@ message Http2ProtocolOptions {
   // `Maximum concurrent streams <https://httpwg.org/specs/rfc7540.html#rfc.section.5.1.2>`_
   // allowed for peer on one HTTP/2 connection. Valid values range from 1 to 2147483647 (2^31 - 1)
   // and defaults to 2147483647.
+  //
+  // For upstream connections, this also limits how many streams Envoy will initiate concurrently
+  // on a single connection. If the limit is reached, Envoy may queue requests or establish
+  // additional connections (as allowed per circuit breaker limits).
   google.protobuf.UInt32Value max_concurrent_streams = 2
       [(validate.rules).uint32 = {lte: 2147483647 gte: 1}];
 

envoy/config/core/v3/protocol.proto

@@ -136,6 +136,10 @@ message Http2ProtocolOptions {
   // `Maximum concurrent streams <https://httpwg.org/specs/rfc7540.html#rfc.section.5.1.2>`_
   // allowed for peer on one HTTP/2 connection. Valid values range from 1 to 2147483647 (2^31 - 1)
   // and defaults to 2147483647.
+  //
+  // For upstream connections, this also limits how many streams Envoy will initiate concurrently
+  // on a single connection. If the limit is reached, Envoy may queue requests or establish
+  // additional connections (as allowed per circuit breaker limits).
   google.protobuf.UInt32Value max_concurrent_streams = 2
       [(validate.rules).uint32 = {lte: 2147483647 gte: 1}];