chore: Simplify extension dependency injection

- Has better typing
- Removes use of unnusual unique symbol
- Fix welcome banner tests
    - Update associated snapshots
- Start converting custom column tests to use ApplicationBuilder
- Remove old and unnused RecursiveTreeView
- Introduce new TreeView for use in CatalogMenu to fix tests

Signed-off-by: Sebastian Malton <sebastian@malton.name>

packages/core/src/common/protocol-handler/router.ts

@@ -201,7 +201,7 @@ export abstract class LensProtocolRouter {
       return name;
     }
 
-    const extension = extensionLoader.getInstanceByName(name);
+    const extension = extensionLoader.getInstanceByName(name) as LensExtension | undefined;
 
     if (!extension) {
       this.dependencies.logger.info(`${LensProtocolRouter.LoggingPrefix}: Extension ${name} matched, but does not have a class for ${ipcRenderer ? "renderer" : "main"}`);