Add simple storage test app

Every time it receives a connection, it will create a file
in TP storage. (todo: allow for creation of files in other
storage areas, multiple files, etc)
Can be run using tipc-test, e.g:
  tipc-test -S com.android.trusty.storagetest -t connect -r 10

Bug: 200034376
Test: run
Change-Id: I0ff444f78b1915e4740dd77a15e577917e38bd2b
4 files changed