Configure CI to use pre-compiled mstest executables

[Arlodotexe]

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:

• Bump MSTest + VSTest and use MSTest.Sdk #203