Update the logic to check if cloud search is enabled

* Instead of using a device config flag to check if search is enabled,
use gantry flag.

* Don't cache if CMP has implemented cloud search because there is no good way to know when the cache becomes invalid.

Bug: 379628729
Test: atest SearchStateTest
Flag: com.android.providers.media.flags.enable_photopicker_search
Change-Id: I0894338f21c871119dc70a37763511489b54fc7e