ANDROID: vendor_hooks: mm: Add tune_swappiness vendor hook in get_swappiness()

Add hook in get_swappiness() for customized swappiness when lru_gen is enabled.

Bug: 299548382
Bug: 453967145
Test: buid pass
Change-Id: If15cb4f71fda6c0b24359f8dc439a090a5434dc9
Signed-off-by: xiaosong.ma <xiaosong.ma@unisoc.com>
(cherry picked from commit bbc9d3bc)
Signed-off-by: Hailong Liu <liuhailong@oppo.com>
(cherry picked from commit b61cb943)