ANDROID: vendor_hooks: account page-mapcount

Support five hooks as follows to account
the amount of multi-mapped pages in kernel:

- android_vh_show_mapcount_pages
- android_vh_do_traversal_lruvec
- android_vh_update_page_mapcount
- android_vh_add_page_to_lrulist
- android_vh_del_page_from_lrulist

Bug: 236578020
Change-Id: Ia2c7015aab442be7dbb496b8b630b9dff59ab935
Signed-off-by: Peifeng Li <lipeifeng@oppo.com>
Signed-off-by: Will McVicker <willmcvicker@google.com>