sysfs: Add (empty) cpu directories for each cpu in /sys/devices/system/cpu.
sysfs: Add (empty) cpu directories for each cpu in /sys/devices/system/cpu.

Numpy needs these.

Also added the "present" directory, since the contents are the same as possible
and online.

PiperOrigin-RevId: 209451777
Change-Id: I2048de3f57bf1c57e9b5421d607ca89c2a173684

google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor