[SettingsProvider] promptly initialize tables for inserts

When DevicePolicyManager creates the work profile, it calls
SettingsProvider put methods for the new user, before SettingsProvider
receives USER_ADDED broadcast. This can cause work profile apps to
disappear in Recent apps. This CL allows SettingsProvider to promptly
set up new tables for the new user before the USER_ADDED broadcast is
received. This will still work with the new ReadWrite lock that we're
introducing to mininize lock contention in SettingsProvider.

BUG: 308397884
Test: manual with TestDPC && create a work profile

Change-Id: Ic256f00b43d605fef16707a9651b9e1255c9475e