use SO_RCVBUFFORCE to force receive buffer increase on Linux (#3804)

* Add ability to force change the receive buffer size using SO_RCVBUFFORCE in Linux

* Fix imports

* Update test

* Add sys_conn_helper_not_linux

* Rename file

* ignore the error on SetReadBuffer

* also run unit tests as root

---------

Co-authored-by: Marten Seemann <martenseemann@gmail.com>

sys_conn_helper_nonlinux.go

@@ -0,0 +1,5 @@
+//go:build !linux
+
+package quic
+
+func forceSetReceiveBuffer(c interface{}, bytes int) error { return nil }