ActivityManager: Include Private Dirty Pages in Meminfo

By using the -p flag, meminfo will include the private dirty pages for each of the processes.
This will help provide mem pages thare are available to only that process and has been modified.

Test: Below are the instructions used for testing
1. Build AOSP for Pixel 5 (redfin)
2. Flash
3. Run adb shell dumpsys meminfo -p
4. View output which includes private dirty information. Snippet below:

...
Total PSS by process:
    251,020K: system (pid 1811)
(   76,888K private dirty)
    150,984K: com.android.systemui (pid 2518)
(   67,020K private dirty)
    142,721K: android.hardware.camera.provider@2.7-service-google (pid 1039)
(   62,636K private dirty)
...

Change-Id: I4da32141edef32b394077d508fb40525d2f6a65e
Signed-off-by: Chirag Modi <cmodi@meta.com>