Sanitize transactions in SSG

When SSG's complete, they send the Transaction to their parent which
could live in another process. This can be problematic if the parent
process has higher privilege than the child and the child added
something into that transaction that only privileged processes can call.
Therefore, sanitize transactions as they cross binder using the calling
uid and pid in case the calling process does have the correct
privileges.

Test: Coming...
Bug: 267794530
Change-Id: Ic0dd2619c22afe57c673c9484b526b841ef1ac99