Configure CI to use pre-compiled mstest executables

## Background

The current CI pipeline rebuilds tests every time they are run, leading to longer build times and reduced efficiency.

## Problem

- Tests are rebuilt from source during every run
- This slows down the overall build process, especially during re-runs after test failure
- Lack of isolated testing environment for CI

## Solution

By using a pre-compiled test executable, we aim to reduce the time it takes for re-runs.

Prerequisites:
- https://github.com/CommunityToolkit/Tooling-Windows-Submodule/pull/203

Review the repository's CI configuration and the prerequisite Tooling-Windows-Submodule pull request #203 first; no specific files or test entry points are named in the issue. Trace where MSTest binaries are built and invoked, then verify that CI runs the pre-compiled executable and that reruns do not rebuild tests.

Scritto dal modello di indicizzazione a partire dal testo della issue.