Proposal: Reduce the number of IPCs in PendingIntent

Several PendingIntent methods are named such that there is very little
hint they involve any IPC, leading devs to overuse them, and thus adds
substantial strain on the system. Caching some of the most used method
results could remove 1000s of unnecessary IPCs.

Bug: 180518680
Test: manual sanity check
Change-Id: I7658251113ebb1e51280a4b8f3b49159d4f764f0