Convert Navigation plugin to Sandy

Summary:
Converted the Navigation plugin to Sandy, and updated Locations bookmark accordingly.
This is a prerequisite step of supporting the bookmarkswidgetin the new AppInspect tab.

Updated LocationsButton accordingly, and overal simplified implementation a bit; locationsbutton now reuses the logic of the NavigationPlugin, rather than reimplemting it. This reduces code duplication and also makes sure the state between plugin and location button stays in sync.

Made sure that search providers are derived and cached rather than stored, again simplifying logic

That being said, the navigation plugin is buggy, but all these things failed before this diff as well:
* No events happening when using iOS, despite the plugin being enabled. But these seems to be a long time know issue, looks like it was never implemented
* Not sure if the parameterized bookmarks is working correctly
* screenshots not always happening at the right time (but fixed a race condition where the wrong bookmark might get updated)
* Locations button doesn't show up if the navigation plugin is supported but not enabled (will try to fix in next diff)

Would be great if bnelo12 could do some exploratory testing to verify what ought to be working, but currently isn't.

Reviewed By: cekkaewnumchai

Differential Revision: D24860757

fbshipit-source-id: e4b56072de8c42af2ada0f5bb022cb9f8c04bb47

desktop/plugins/navigation/util/indexedDB.tsx

@@ -88,7 +88,7 @@ export const readBookmarksFromDB: () => Promise<Map<string, Bookmark>> = () => {
   });
 };
 
-export const removeBookmark: (uri: string) => Promise<void> = (uri) => {
+export const removeBookmarkFromDB: (uri: string) => Promise<void> = (uri) => {
   return new Promise<void>((resolve, reject) => {
     openNavigationPluginDB()
       .then((db: IDBDatabase) => {