DNS DoH: Use Chrome's fingerprint & keepAlivePeriod, Add header padding by default

https://github.com/XTLS/Xray-core/discussions/4430#discussioncomment-12374292

common/net/net.go

@@ -1,2 +1,14 @@
 // Package net is a drop-in replacement to Golang's net package, with some more functionalities.
 package net // import "github.com/xtls/xray-core/common/net"
+
+import "time"
+
+// defines the maximum time an idle TCP session can survive in the tunnel, so
+// it should be consistent across HTTP versions and with other transports.
+const ConnIdleTimeout = 300 * time.Second
+
+// consistent with quic-go
+const QuicgoH3KeepAlivePeriod = 10 * time.Second
+
+// consistent with chrome
+const ChromeH2KeepAlivePeriod = 45 * time.Second