tls: split client/server defaults. (#5392)

No functional changes.

Signed-off-by: Piotr Sikora <piotrsikora@google.com>

Mirrored from https://github.com/envoyproxy/envoy @ 58bf369ab877058f7ee24d1ed9212b26a7f04c41

envoy/api/v2/auth/cert.proto

@@ -33,10 +33,10 @@ message TlsParameters {
     TLSv1_3 = 4;
   }
 
-  // Minimum TLS protocol version.
+  // Minimum TLS protocol version. By default, it's ``TLSv1_0``.
   TlsProtocol tls_minimum_protocol_version = 1 [(validate.rules).enum.defined_only = true];
 
-  // Maximum TLS protocol version.
+  // Maximum TLS protocol version. By default, it's ``TLSv1_2``.
   TlsProtocol tls_maximum_protocol_version = 2 [(validate.rules).enum.defined_only = true];
 
   // If specified, the TLS listener will only support the specified `cipher list