Add procrank2

Implement procrank using new libmeminfo APIs. procrank2 is functionally
equivalent to procrank except for the part where the old procrank would
print processes under each oomadj level if called with 'procrank -c -o'.

The output format of 'procrank2' is identical to that of 'procrank'.
'procrank2' also gives significant performance boost over 'procrank' but
does cost a more memory as the library is written to 99% use case where
callers almost always want to read the memory usage of hte process.

Bug: 114325007
Bug: 111694435
Test:
     # adb push /google/data/ro/users/ss/sspatil/test-memutils.sh /data/local/tmp/
     # adb push procmem2 /data/local/tmp && adb push procrank2 /data/local/tmp
     # adb root && adb shell
     $ cd /data/local/tmp/
     $ chmod +x test-memutils.sh
     $ ./test-memutils.sh 2>&1 | tee test.log
Test:
  procrank:
    0m00.43s real     0m00.11s user     0m00.32s system
  procrank2:
    0m00.42s real     0m00.05s user     0m00.36s system

Change-Id: I37b71a4625248e333ba01801c0d8d7ef348e4cfa
Signed-off-by: Sandeep Patil <sspatil@google.com>