Indexing cancelation is not cleaned up properly

Steps to reproduce:

1. Create and open a new Universal 3D Project
2. Observe the Background Tasks loading in the bottom right corner of the Editor and click the blue loading bar to open the Background Tasks Window
3. Cancel Search Indexing
4. Open the Search Window (Ctrl + K)
5. Observe the Indexing Banner at the top of the Search Window

Actual results: Indexing banner is shown and says "Indexing is in progress" and user can not restart indexing

Expected results: cancellation should be cleaned up properly and user can choose to restart indexing or use current indexation for search 

Reproducible with versions: 6000.5.0a7, 6000.5.0b1, 6000.6.0a1

Can’t test with versions: 6000.0.71f1, 6000.3.12f1, 6000.4.1f1, 6000.5.0a6 (No Banner feature)

Tested on (OS): Windows 11