[DocsUI, Search]: Check validity of constructor arguments.

For search loaders we need either the query or recency. Without those,
we run the risk of returning large number of results. A check is added
to the SearchLoader and it is tested in the unit test.

Test: m DocumentsUIGoogle
Bug: 378590632
Change-Id: Ic9dc17d676b444a18b0159c5ad29fedf518780c6
Flag: com.android.documentsui.flags.use_search_v2