Reduce extra binder call for take task snapshot.

It is not necessary to take the task snapshot from the Shell because
it is usually executed in the SystemUI process. The Launcher can perform
the same operation through ActivityManagerWrapper. Which can also help
release the memory since it won't referened by 3 processes.

Flag: EXEMPT bugfix
Bug: 238206323
Test: close task from recents, verify SystemUI won't hold the
snapshot memory

Change-Id: Ib726d3a70f5f2aa33f32b7dc189e7b7a8c2dd1b1