libhealthloop: Only wake up for power supply events

healthd receives power supply information as uevents and holds a
wakelock while receiving these uevents. Without uevent filter, suspend
is postponed indefinitely if a uevent is generated during suspend. Fix
this by attaching a BPF program to the uevent socket that filters out
all events that are not power supply events.

This CL replaces the following CLs:
* Lianwei Wang, healthd: Don't set all eventpoll wakeup-able,
  2015-07-09
  (https://android-review.googlesource.com/c/platform/system/core/+/158851

).
* Stephane Lee, Add BPF filter to filter uevents for
  SUBSYSTEM=powersupply, 2022-05-06.

Multiple ideas and some code in this CL have been borrowed from
Stephane Lee's CL.

Bug: 139203596
Bug: 140330870
Bug: 203131934
Bug: 203229817
Bug: 203462310
Bug: 221725014
Test: Verified that a Pixel 2024 still wakes up if a USB cable is connected or disconnected.
Test: Verified that suspend and resume still works for a Pixel 2024 device.
Test: Verified that the following text appears in the Cuttlefish logcat output: "HealthLoop: Successfully attached BPF program to uevent socket"
Test: Verified as follows that recovery mode works fine with Cuttlefish: adb reboot recovery && adb root && adb shell dmesg | grep -E 'F DEBUG|HealthLoop'
Change-Id: I64446b103d660d220880461bdef7ef0f531e1734
Signed-off-by: Bart Van Assche <bvanassche@google.com>