ANDROID: vendor_hook: Add hook is to optimize the time consumption of shrink slab

one Vendor hook add:
    android_vh_do_shrink_slab_ex

Add vendor hook point in do_shrink_slab to optimize for user
experience related threads and time-consuming shrinkers.

Bug: 399777353
Bug: 400818928
Bug: 401099893

Change-Id: I63778c73f76930fe27869e33ba6cdb97d50cf543
Signed-off-by: pengzhongcui <pengzhongcui@xiaomi.corp-partner.google.com>
(cherry picked from commit 05ab4ba8)