Different approach: add a PacketNumberSpace #220

Job	Run time
msrv	1m 5s
test (ubuntu-latest, stable)	1m 28s
test (ubuntu-latest, beta)	1m 26s
lint	40s
audit	28s
test (macos-latest, stable)	1m 17s
test-android (x86_64-linux-android, x86_64, 26)	2m 31s
test (windows-latest, stable)	3m 59s
test-aws-lc-rs	55s
test-android (x86_64-linux-android, x86_64, 25)	2m 14s
test-android (i686-linux-android, x86, 26)	3m 28s
test on freebsd	6h 0m 0s
test-android (i686-linux-android, x86, 25)	3m 41s
test on illumos	7m 15s
test on netbsd	5m 42s
test on solaris	21m 29s
test wasm32-unknown-unknown	56s
	6h 58m 34s

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