Expose app resume times to the ApplicationProvider.

Add ActivityManager.getAllPackageUsageStats which returns
the PkgUsageStats object for all packages.

In UsageStatsService, remember the last resume time of each component, and
add that info to PkgUsageStats instances.

ApplicationProvider will use getAllPackageUsageStats and the new field
in PkgUsageStats to set the new SearchManager column
SUGGEST_COLUMN_LAST_USAGE_HINT for requests with the GLOBAL_SEARCH
permission.

Change-Id: I80e9b127410ed0d528515d2256787f30a953e9b0