Enable column selection and sorting in DocumentsTab (with persistence) with improvements (#1963)

* Reapply "Enable column selection and sorting in DocumentsTab (with persistence) (#1881)" (#1960)

This reverts commit fe9730206e.

* Fix logic bug: always include defaultQueryFields in query.

* Show resize column option outside of feature flag

* Improve prevention of no selected columns

* Add more unit tests

* Fix styling on table

* Update test snapshots

* Remove "sortable" property on table which makes the header cell focusable (user sorts by selecting menu item, not by clicking on cell)

src/Platform/Hosted/extractFeatures.ts

@@ -38,6 +38,7 @@ export type Features = {
   readonly copilotChatFixedMonacoEditorHeight: boolean;
   readonly enablePriorityBasedExecution: boolean;
   readonly disableConnectionStringLogin: boolean;
+  readonly enableDocumentsTableColumnSelection: boolean;
 
   // can be set via both flight and feature flag
   autoscaleDefault: boolean;
@@ -108,6 +109,7 @@ export function extractFeatures(given = new URLSearchParams(window.location.sear
     copilotChatFixedMonacoEditorHeight: "true" === get("copilotchatfixedmonacoeditorheight"),
     enablePriorityBasedExecution: "true" === get("enableprioritybasedexecution"),
     disableConnectionStringLogin: "true" === get("disableconnectionstringlogin"),
+    enableDocumentsTableColumnSelection: "true" === get("enabledocumentstablecolumnselection"),
   };
 }