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/browser/modal/media/modal.css

@@ -27,7 +27,7 @@
 	padding: 15px;
 }
 
-.modal .icon.in-progress {
+.modal .codicon.in-progress {
 	width: 25px;
 	height: 25px;
 }

src/sql/workbench/browser/modal/modal.ts

@@ -240,7 +240,7 @@ export abstract class Modal extends Disposable implements IThemable {
 		if (!this._modalOptions.isAngular) {
 			this._modalFooterSection = DOM.append(modalContent, DOM.$('.modal-footer'));
 			if (this._modalOptions.hasSpinner) {
-				this._spinnerElement = DOM.append(this._modalFooterSection, DOM.$('.icon.in-progress'));
+				this._spinnerElement = DOM.append(this._modalFooterSection, DOM.$('.codicon.in-progress'));
 				DOM.hide(this._spinnerElement);
 			}
 			this._leftFooter = DOM.append(this._modalFooterSection, DOM.$('.left-footer'));