Inform temp-allowlist changes from AMS to NPMS asynchronously.

Currently, the callback to NPMS gets triggered from the AMS
handler. So technically, this codepath is already asynchronous.
But this change updates the callback to be called from a non-UI
thread, as some of the NPMS operations could take a while to
complete.

Bug: 283182341
Test: atest CtsHostsideNetworkTests
Change-Id: Ibbf270b46bb3a0df8d8ba759718bb378cca90063