libbinder: stability check moved to trans time

Before: stability check done when binder is read from a parcel
After: stability check done when binder is transacted on

Why this change is being made/benefits:
- vendor binders can be used as tokens in system context
- pingBinder/interfaceChain/etc.. can be done on vendor binders in a
system context, so code can generically operate on binders. This is
particularly useful for service manager and dumpstate, which previously
I was going to special-case
- policy on which binders go where is entirely reliant on SELinux
whereas before there were additional runtime restrictions

Cons to this change:
- allowed binders must be determined by context. BpBinder now checks
stability based on kLocalStability. More work would need to be done to
get this working with APEX.

Bug: 136027762
Test: binderStabilityTest
Change-Id: Iff026e81a130dbb8885ca82ec24e69a5768847eb
Merged-In: Iff026e81a130dbb8885ca82ec24e69a5768847eb