runsettings are ignored during test discovery (data driven tests)

[rdstevens-gh]

Describe the bug

During test discovery of DynamicData tests (using the ITestDataSource), the <EnvironmentVariables> section of the selected .runsettings file is ignored.

Steps To Reproduce

1. Implement the following:

    internal class ExampleTestDataSource : Attribute, ITestDataSource
    {
        public IEnumerable<object?[]> GetData(MethodInfo methodInfo)
        {
            yield return new object[] { Environment.GetEnvironmentVariable("TEST_ENV") };
        }

        public string? GetDisplayName(MethodInfo methodInfo, object?[]? data)
        {
            if (data != null)
            {
                var value = (string)data[0];
                return $"{methodInfo.Name} - {value}";
            }
            return null;
        }
    }

    [TestClass]
    public class MyTests
    {
        [TestMethod]
        [ExampleTestDataSource]
        public void MyTest(string name)
        {
            Assert.IsTrue(!string.IsNullOrEmpty(name));
        }
    }

2. Create a .runnsettings file with the following section:

<RunSettings>
	<RunConfiguration>
		<EnvironmentVariables>
			<TEST_ENV>This is a string</TEST_ENV>
		</EnvironmentVariables>
	</RunConfiguration>
</RunSettings>

3. Configure TestExplorer to use your .runsettings file.

4. Observe that the test name (in test explorer) does not include the "This is a string" token.

5. Observe that MyTest fails.

Expected behavior

.Runsettings to be used during test discovery.

Actual behavior

.runsettings is ignored during test discovery.

[Youssef1313]

The issue here is in VSTestBridge. The RunSettingsEnvironmentVariableProvider implementation doesn't consider TESTINGPLATFORM_EXPERIMENTAL_VSTEST_RUNSETTINGS.