feat: add `swapOnlyUsage` in `MemoryStats` #5191

Job	Run time
cross-i386	1m 33s
cross-i386 (runc_nodmz)	1m 55s
test (ubuntu-20.04, 1.20.x, rootless, -race)	7m 31s
test (ubuntu-20.04, 1.20.x, rootless)	7m 31s
test (ubuntu-20.04, 1.20.x, -race)	7m 16s
test (ubuntu-20.04, 1.20.x)	5m 56s
test (ubuntu-20.04, 1.21.x, rootless, -race)	9m 13s
test (ubuntu-20.04, 1.21.x, rootless)	7m 19s
test (ubuntu-20.04, 1.21.x, -race)	6m 57s
test (ubuntu-20.04, 1.21.x)	7m 15s
test (ubuntu-20.04, 1.21.x, criu-dev)	7m 32s
test (ubuntu-22.04, 1.20.x, rootless, -race)	11m 5s
test (ubuntu-22.04, 1.20.x, rootless, -race, runc_nodmz)	11m 25s
test (ubuntu-22.04, 1.20.x, rootless)	11m 6s
test (ubuntu-22.04, 1.20.x, rootless, runc_nodmz)	11m 10s
test (ubuntu-22.04, 1.20.x, -race)	9m 43s
test (ubuntu-22.04, 1.20.x, -race, runc_nodmz)	8m 48s
test (ubuntu-22.04, 1.20.x)	7m 8s
test (ubuntu-22.04, 1.20.x, runc_nodmz)	7m 26s
test (ubuntu-22.04, 1.21.x, rootless, -race)	12m 3s
test (ubuntu-22.04, 1.21.x, rootless, -race, runc_nodmz)	11m 4s
test (ubuntu-22.04, 1.21.x, rootless)	10m 48s
test (ubuntu-22.04, 1.21.x, rootless, runc_nodmz)	10m 49s
test (ubuntu-22.04, 1.21.x, -race)	8m 42s
test (ubuntu-22.04, 1.21.x, -race, runc_nodmz)	9m 56s
test (ubuntu-22.04, 1.21.x)	7m 18s
test (ubuntu-22.04, 1.21.x, runc_nodmz)	9m 20s
test (ubuntu-22.04, 1.21.x, criu-dev)	7m 55s
	3h 55m 44s

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