Add a test wakeupclient service implementation.

The test implementation will send out a remote task to remote access
HAL every 5s.

Test: Manually test on gcar_emu.
adb root
adb remount
adb reboot
adb root
adb remount
m -j TestWakeupClientServer
cd out/target/product/emulator_car64_x86_64
adb push ./vendor/bin/TestWakeupClientServer /vendor/bin
adb shell

In the shell:
su
/vendor/bin/TestWakeupClientServer

Check adb logcat, verify tasks are received.
Bug: 246841306

Change-Id: Idaf198662f7004e3a9e77d75caeffc00cda49218