kqueue: make changelist and eventlist of kevent share the same array The array used by the changelist of the kevent() can be reused by the eventlist, We should make use of this feature to eliminate the extra overhead of array allocation. https://man.freebsd.org/cgi/man.cgi?kqueue https://developer.apple.com/library/archive/documentation/System/Conceptual/ManPages_iPhoneOS/man2/kqueue.2.html https://leaf.dragonflybsd.org/cgi/web-man?command=kqueue§ion=2 https://man.netbsd.org/kqueue.2 https://man.openbsd.org/kqueue.2 --------- Signed-off-by: Andy Pan <i@andypan.me>