Adding wizard and dialog footer loading spinner (#21230)

* Adding wizard and dialog loading

* Moving apis to proposed

* fixing namespace

* Only firing event when the value changes

* Only firing when value is changed

* Adding loading complete message to dialog and wizard

* Registering listeners and making a new base interface for loading components

* Fixing api comment

* Renaming prop to loadingCompleted

* old loading icon

src/sql/workbench/test/electron-browser/api/mainThreadModelViewDialog.test.ts

@@ -136,7 +136,10 @@ suite('MainThreadModelViewDialog Tests', () => {
 			okButton: okButtonHandle,
 			cancelButton: cancelButtonHandle,
 			customButtons: [button1Handle, button2Handle],
-			message: undefined
+			message: undefined,
+			loading: false,
+			loadingText: undefined,
+			loadingCompletedText: undefined,
 		};
 
 		// Set up the wizard details
@@ -183,7 +186,10 @@ suite('MainThreadModelViewDialog Tests', () => {
 			pages: [page1Handle, page2Handle],
 			message: undefined,
 			displayPageTitles: false,
-			width: 'wide'
+			width: 'wide',
+			loading: false,
+			loadingText: undefined,
+			loadingCompletedText: undefined
 		};
 
 		// Register the buttons, tabs, and dialog