Nasc/delete instance code removal (#12307)

* Formatted page

* Removed ResourceHealthPage from the dashboard

* Deleted files that no longer applies to the public preview backend

* shouldn't be able to open the postgres dashboard

extensions/azdata/src/typings/azdata-ext.d.ts

@@ -228,6 +228,7 @@ declare module 'azdata-ext' {
 			},
 			postgres: {
 				server: {
+					delete(name: string): Promise<AzdataOutput<void>>,
 					list(): Promise<AzdataOutput<PostgresServerListResult[]>>,
 					show(name: string): Promise<AzdataOutput<PostgresServerShowResult>>,
 					edit(args: {