[Android O] /proc/stat is no longer accessible in Android O

[Manabu-GT]

https://issuetracker.google.com/issues/37140047 confirms that /proc/stat was removed from Android O as intended. Well, makes sense from the security perspective.

Note: /proc/self/stat seems to still work.

[Manabu-GT]

https://developer.android.com/reference/android/os/HardwarePropertiesManager.html might be useful, but need to check what it could return.
->It turns out that accessing it requires being a device owner or holding the DEVICE_POWER permission which is only for system apps.

Looks like CpuUsageModule needs to be deprecated and will be just a no-op for O and above.

[Manabu-GT]

Similary, /sys/devices/system/cpu/cpu[num]/cpufreq/scaling_cur_freqand/sys/devices/system/cpu/cpu[num]/cpufreq/cpuinfo_max_freq` are not accessible, too.