Telltales example documentation needs update

In the current implementation, we are having only one telltales example which works on host and target platforms. In the documentation there is mentioned that we have a separate version for each platform:

https://doc-snapshots.qt.io/qtsaferenderer/qtsaferenderer-examples.html

Also, the telltales example is currently tied with the qtcluster demo and cannot be used with the indicators as earlier.

I've done the change to the indicators that it can be run as a standalone safe UI application without telltales:

https://codereview.qt-project.org/c/tqtc-boot2qt/qtsaferenderer/+/325397