[Regression] DynamicDataAttribute.GetData no longer works in 3.7 when using TestFramework without TestAdapter

[Youssef1313]

This regression is likely caused by #3801

In this PR, pay attention to the change in DynamicDataAttribute.cs.

Before the changes, DynamicDataAttribute.GetData would always work and use reflection.

After the change, DynamicDataAttribute will use DynamicDataProvider.Instance.GetData, but DynamicDataProvider.Instance is set by the adapter. So, when the adapter isn't used, this fails because DynamicDataProvider.Instance is null:

testfx/src/TestFramework/TestFramework/Attributes/DataSource/DynamicDataProvider.cs

Lines 12 to 14 in f2de560

	get => s_dynamicDataOperations
	?? throw new InvalidOperationException($"Dynamic data provider is not set, it should be set by MSTest adapter. " +
	$"If you are seeing this error, you are using Test Framework without Test Adapter, and your adapter should set {nameof(DynamicDataProvider)}.{nameof(Instance)}. In MSTestAdapter, this happens when PlatformServiceProvider.Instance is called.");

Worse, the exception says:

If you are seeing this error, you are using Test Framework without Test Adapter, and your adapter should set DynamicDataProvider.Instance

However, DynamicDataProvider is even internal.

AB#2342253

[Youssef1313]

Actually, SourceGeneratedDynamicDataOperations seems to be doing nothing. It's inheriting DynamicDataOperations without any additional functionality.

[Youssef1313]

@Evangelink Adding to 3.7.1 for now. We will discuss on Monday depending on how much time is needed to fix and will evaluate if we make it part of 3.7.1, or if we will not delay 3.7.1 further and make this part of 3.7.2