meminfo: Debug: Use libmeminfo to read process maps

This is the last bit of android_os_Debug functions that are now
converted to using libmeminfo. The rest are to do with memtrack and they
will be handled separately with the Ion fdinfo changes.

Bug: 111694435
Test: runtest --path \
      frameworks/base/core/tests/coretests/src/com/android/internal/os/DebugTest.java
Test: adb root && adb shell dumpsys meminfo -a system_server
Test: adb shell dumpsys meminfo -a <app name>

Change-Id: Iea3439979858ae7eac68cfbd0dd3450b7c65a8bf
Signed-off-by: Sandeep Patil <sspatil@google.com>