ActivityManager: kill frozen processes receiving sync transactions

Synchronous transactions to frozen processes are rejected by binder,
which can potentially leave these processes in an unclean state when
unfrozen. Kill such processes insted of unfreezing then when they're
removed from the cache. This patch also increases the timeout before
freezing an app, to allow pending transactions to be processes for
a longer window after caching and so to reduce the amount of background
kills.

Bug: 143717177
Test: cached/frozen a few apps, sent sync and async transactions to them
and verified that killing happened when expected.

Change-Id: Ieca9d49e1befd1358862aa7afeeec15a408d7ef3