Fix errors due to icon to codicon rename in VSCode (#7837)

Found numerous errors where icons weren't rendering correctly.
- Anything that's an action must have CSS using "codicon" not "icon"
since VSCode sets the "codicon" class automatically.
This affected Agent view in particular, but also:
  - acounts view
  - new tab view in dashboard
 - many more
- Anything referencing the common-icons.css icons needed updating.
This hid help tooltip text in FormContainer UI for example.
- Finally I tried to convert all references from icon -> codicon,
even when the CSS was technically correct. This was done
for maintainability reasons - from now on always add codicon.

Fixes #7827

src/sql/workbench/services/dashboard/browser/newDashboardTabDialogImpl.ts

@@ -53,7 +53,7 @@ interface ExtensionListTemplate {
 class ExtensionListRenderer implements IListRenderer<IDashboardUITab, ExtensionListTemplate> {
 	public static TEMPLATE_ID = 'extensionListRenderer';
 	private static readonly OPENED_TAB_CLASS = 'success';
-	private static readonly ICON_CLASS = 'extension-status-icon icon';
+	private static readonly ICON_CLASS = 'extension-status-icon codicon';
 
 	public get templateId(): string {
 		return ExtensionListRenderer.TEMPLATE_ID;
@@ -62,7 +62,7 @@ class ExtensionListRenderer implements IListRenderer<IDashboardUITab, ExtensionL
 	public renderTemplate(container: HTMLElement): ExtensionListTemplate {
 		const tableTemplate: ExtensionListTemplate = Object.create(null);
 		tableTemplate.root = DOM.append(container, DOM.$('div.list-row.extensionTab-list'));
-		tableTemplate.icon = DOM.append(tableTemplate.root, DOM.$('div.icon'));
+		tableTemplate.icon = DOM.append(tableTemplate.root, DOM.$('div.codicon'));
 		let titleContainer = DOM.append(tableTemplate.root, DOM.$('div.extension-details'));
 		tableTemplate.title = DOM.append(titleContainer, DOM.$('div.title'));
 		tableTemplate.description = DOM.append(titleContainer, DOM.$('div.description'));