northd: Generate router's stateful flows using lr_stateful data. #3644

Job	Run time
dpdk gcc	8s
osx clang --disable-ssl	3m 51s
linux rpm fedora	7m 13s
linux gcc --disable-ssl	1m 55s
linux clang --disable-ssl	1m 58s
linux gcc test -300	8m 26s
linux gcc test 301-600	5m 36s
linux gcc test 601- unstable	4m 55s
linux clang test sanitizers -300	11m 32s
linux clang test sanitizers 301-600	8m 11s
linux clang test sanitizers 601- unstable	8m 45s
linux gcc test -ljemalloc -300	8m 41s
linux gcc test -ljemalloc 301-600	5m 39s
linux gcc test -ljemalloc 601- unstable	5m 17s
linux gcc system-test-dpdk dpdk -100	12m 52s
linux gcc system-test-dpdk dpdk 101- unstable	12m 3s
linux gcc system-test-userspace -100	11m 22s
linux gcc system-test-userspace 101- unstable	10m 57s
linux gcc system-test -100	14m 6s
linux gcc system-test 101- unstable	12m 42s
linux clang system-test sanitizers -100	15m 51s
linux clang system-test sanitizers 101- unstable	14m 8s
linux x86 gcc --disable-ssl	1m 50s
	3h 7m 58s

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