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/base/browser/ui/breadcrumb/breadcrumb.component.ts

@@ -19,12 +19,12 @@ import { subscriptionToDisposable } from 'sql/base/browser/lifecycle';
 				<span style="display: flex; flex-flow: row; align-items: center; margin: 10px">
 					<ng-template ngFor let-item let-first="first" let-last="last" [ngForOf]="menuItems">
 						<span style="padding: 5px; display: flex; align-items: center">
-							<span *ngIf="item.icon" class="icon" style="display: inline-block; margin-right: 5px" [ngClass]="item.icon"></span>
+							<span *ngIf="item.icon" class="codicon" style="display: inline-block; margin-right: 5px" [ngClass]="item.icon"></span>
 							<span *ngIf="first">{{item.label}}</span>
 							<span *ngIf="last" style="">{{item.label}}</span>
 							<a class="router-link" *ngIf="!last && !first" (click)="route(item.routerLink)" >{{item.label}}</a>
 						</span>
-						<span *ngIf="!last" class="icon chevron-right"></span>
+						<span *ngIf="!last" class="codicon chevron-right"></span>
 					</ng-template>
 				</span>
 				`