Running MTP tests from Visual Studio Test Explorer does not honor `launchsettings.json`

[julealgon]

Describe the bug

When running MTP tests from the VS UI (via Test Explorer), the runner doesn't honor existing launchsettings.json files.

launchsettings.json is honored today via dotnet test.

Version used

MTP 2.3.3
Visual Studio 18.10.0

Steps To Reproduce

1. Create a new MTP-based test project
2. Create/edit a launch profile to generate a launchsettings.json
3. Set an environment variable on launchsettings.json
4. Run a test via Test Explorer
5. Note the env var is not honored

Expected behavior

Launching a test through Test Explorer should respect launchsettings.json the same way dotnet test does.

Actual behavior

launchsettings.json is ignored.

Additional context