allow extension to provide custom icons to data explorer tree (#16868)

* expose icon path to extension for OE node

* remove node type

* pr comments

src/sql/workbench/api/common/sqlExtHostTypes.ts

@@ -5,6 +5,7 @@
 
 import { nb, IConnectionProfile } from 'azdata';
 import * as vsExtTypes from 'vs/workbench/api/common/extHostTypes';
+import { URI } from 'vs/base/common/uri';
 
 // SQL added extension host types
 export enum ServiceOptionType {
@@ -447,6 +448,9 @@ export class TreeItem extends vsExtTypes.TreeItem {
 	providerHandle?: string;
 }
 
+export type ThemedIconPath = { light: string | URI; dark: string | URI };
+export type IconPath = string | URI | ThemedIconPath;
+
 export class SqlThemeIcon {
 
 	static readonly Folder = new SqlThemeIcon('Folder');