Initial Fabric support (#1607)

* Add Platform.Fabric to run in context of Fabric

* Use separate StyleConstants

We want to have more flexibility with Styles at runtime
but Constants depend on ConfigContext and therefore
get loaded very early at startup.

* Add Fabric specific styles and Fluent theme

documentDBFabric.less contains all styles for Fabric.
We use React.lazy to import them conditionally at
runtime preventing webpack from preprocessing
them into main.css.

* Restyle CommandBar for Fabric
with more roundness and native colors.

* Disable Notebooks when running in Fabric

* Disable Synapse and Scripts commands for Fabric

* Fix code formatting issues

* Fetch encrypted token from sessionStorage for fabric platform

* Fix Tabs style

* Dark refresh icons for Fabric

* Use new ResourceTree2 for Fabric

* Fluent tree should have a fixed width
otherwise the action buttons jump around on hover.

* Disable remaining Script actions in Fabric

* Revert accidentally committed change
which broke a test

* Fix cross-origin error second try

* Adjust @FabrixBoxMargin css

* Hide Database Scale node on Fabric

* Remove all Collection child nodes on Fabric

* Add a comment about why we need FabricPlatform.tsx

* Fix equality checks

* Fix more Colors for Fabric

* Switch resource tree to "medium" size

* Fix formatting again

* Fix formatting again

* Disable no-var-requires error on some intended var import.

* Increase memory limit for build

* Use standard Segoe UI font for Fabric

* Improve Tabs design for Fabric

* Fix active Tab style bug in Portal
introduced with 39a7765aef

---------

Co-authored-by: Laurent Nguyen <laurent.nguyen@microsoft.com>

src/Explorer/Menus/CommandBar/CommandBarUtil.tsx

@@ -9,7 +9,9 @@ import {
 import * as React from "react";
 import _ from "underscore";
 import ChevronDownIcon from "../../../../images/Chevron_down.svg";
-import { PoolIdType, StyleConstants } from "../../../Common/Constants";
+import { PoolIdType } from "../../../Common/Constants";
+import { StyleConstants } from "../../../Common/StyleConstants";
+import { configContext, Platform } from "../../../ConfigContext";
 import { Action, ActionModifiers } from "../../../Shared/Telemetry/TelemetryConstants";
 import * as TelemetryProcessor from "../../../Shared/Telemetry/TelemetryProcessor";
 import { CommandButtonComponentProps } from "../../Controls/CommandButton/CommandButtonComponent";
@@ -24,11 +26,14 @@ import { MemoryTracker } from "./MemoryTrackerComponent";
 export const convertButton = (btns: CommandButtonComponentProps[], backgroundColor: string): ICommandBarItemProps[] => {
   const buttonHeightPx = StyleConstants.CommandBarButtonHeight;
 
+  const hoverColor =
+    configContext.platform == Platform.Fabric ? StyleConstants.FabricAccentLight : StyleConstants.AccentLight;
+
   const getFilter = (isDisabled: boolean): string => {
     if (isDisabled) {
       return StyleConstants.GrayScale;
     }
-    return undefined;
+    return configContext.platform == Platform.Fabric ? StyleConstants.NoColor : undefined;
   };
 
   return btns
@@ -68,6 +73,7 @@ export const convertButton = (btns: CommandButtonComponentProps[], backgroundCol
               height: buttonHeightPx,
               paddingRight: 0,
               paddingLeft: 0,
+              borderRadius: configContext.platform == Platform.Fabric ? StyleConstants.FabricButtonBorderRadius : "0px",
               minWidth: 24,
               marginLeft: isSplit ? 0 : 5,
               marginRight: isSplit ? 0 : 5,
@@ -79,17 +85,17 @@ export const convertButton = (btns: CommandButtonComponentProps[], backgroundCol
             splitButtonMenuButton: {
               backgroundColor: backgroundColor,
               selectors: {
-                ":hover": { backgroundColor: StyleConstants.AccentLight },
+                ":hover": { backgroundColor: hoverColor },
               },
               width: 16,
             },
             label: { fontSize: StyleConstants.mediumFontSize },
-            rootHovered: { backgroundColor: StyleConstants.AccentLight },
-            rootPressed: { backgroundColor: StyleConstants.AccentLight },
+            rootHovered: { backgroundColor: hoverColor },
+            rootPressed: { backgroundColor: hoverColor },
             splitButtonMenuButtonExpanded: {
               backgroundColor: StyleConstants.AccentExtra,
               selectors: {
-                ":hover": { backgroundColor: StyleConstants.AccentLight },
+                ":hover": { backgroundColor: hoverColor },
               },
             },
             splitButtonDivider: {
@@ -120,7 +126,7 @@ export const convertButton = (btns: CommandButtonComponentProps[], backgroundCol
                 // TODO Remove all this crazy styling once we adopt Ui-Fabric Azure themes
                 selectors: {
                   ".ms-ContextualMenu-itemText": { fontSize: StyleConstants.mediumFontSize },
-                  ".ms-ContextualMenu-link:hover": { backgroundColor: StyleConstants.AccentLight },
+                  ".ms-ContextualMenu-link:hover": { backgroundColor: hoverColor },
                   ".ms-ContextualMenu-icon": { width: 16, height: 16 },
                 },
               },