pm install-commit supports waiting for staged session to be ready

This change allows callers of adb install-multi-package to benefit from
--wait flag which will wait for the pre-installed verification of staged
sessions.

Test: atest PackageManagerShellCommandTest
Test: adb install-multi-package tzdata.apex shim.apex
Bug: 147694315
Change-Id: Ia356c4dff635ec230eb505fb400913c76ec84042