Fixes #4300 - Scrolling intermittently causes All_Scenarios_Quit_And_Init_Shutdown_Properly to fail (#4301)

* Refactor Scrolling.cs for timer management and nullability

Enabled nullable reference types with `#nullable enable` for improved safety. Replaced the `pulsing` flag with a new `_progressTimer` object to better manage the progress bar's timer lifecycle. Updated `AppOnInitialized` and `AppUnloaded` methods to handle timer initialization and cleanup properly, preventing potential memory leaks.

Simplified code by removing unnecessary comments and aligning method signatures with nullable reference type annotations.

* Enable nullable types and add debugging utilities

* Runu tests 5 times

* Adjust abortTime in ScenarioTests to 1800

* Revert "Runu tests 5 times"

This reverts commit b9b5282315.

* Improve CI diagnostics and adjust scenario abort time

* Fix typos, update metadata,

Corrected typos in `ScenarioCategory` and comments in `Mazing.cs`.
Added the `System.Text` namespace to support additional functionality.
Introduced a new "Games" category in `ScenarioCategory`.
Updated `.DotSettings` to include "Mazing" in the user dictionary.
Improved overall code comments and metadata for clarity.

* Remove unnecessary null assertion for _progressTimer

* Update Examples/UICatalog/Scenarios/Scrolling.cs

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

.github/workflows/integration-tests.yml

@@ -47,8 +47,6 @@ jobs:
       run: |
        dotnet test Tests/IntegrationTests --no-build --verbosity normal --diag:logs/${{ runner.os }}/logs.txt --blame --blame-crash --blame-hang --blame-hang-timeout 60s --blame-crash-collect-always -- xunit.stopOnFail=true
      
-       # mv -v Tests/IntegrationTests/TestResults/*/*.* TestResults/IntegrationTests/
-
     - name: Upload Test Logs
       if: always()
       uses: actions/upload-artifact@v4