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/parts/dataExplorer/browser/media/connectionViewletPanel.css

@@ -108,8 +108,8 @@ margin-bottom: 2px;
 }
 
 /* loading for OE node */
-.server-explorer-viewlet .monaco-tree .monaco-tree-rows > .monaco-tree-row > .icon.in-progress .connection-tile:before,
-.server-explorer-viewlet .monaco-tree .monaco-tree-rows > .monaco-tree-row > .icon.in-progress .object-element-group:before {
+.server-explorer-viewlet .monaco-tree .monaco-tree-rows > .monaco-tree-row > .codicon.in-progress .connection-tile:before,
+.server-explorer-viewlet .monaco-tree .monaco-tree-rows > .monaco-tree-row > .codicon.in-progress .object-element-group:before {
 	position: absolute;
 	display: block;
 	width: 36px;
@@ -129,4 +129,4 @@ margin-bottom: 2px;
 /* Add connection button */
 .server-explorer-viewlet .button-section {
 	padding: 20px;
-}
+}