Update TransformCollectionAndObjectInitializers to check for init-only properties

[nikitalita]

Problem

Fixes #3677

Solution

The main culprit was here:

					if (newObjInst.ILStackWasEmpty && v.Kind == VariableKind.Local
						&& !currentMethod.IsConstructor
						&& !currentMethod.IsCompilerGeneratedOrIsInCompilerGeneratedClass())

Adding a simple check to see if the declaring type has init-only properties fixes the issue.

I would add a test that covers this, but I do not know how to force the C# compiler to allocate an object locally instead of on the stack consistently; if you have any tips, let me know.

[siegfriedpammer]

I would add a test that covers this, but I do not know how to force the C# compiler to allocate an object locally instead of on the stack consistently; if you have any tips, let me know.

I couldn't find a definitive rule for when the Roslyn compiler uses local slots over stack slots. The main observation is that Roslyn prefers stack over locals especially in Release builds.

Some of the things just cannot be tested in C# pretty tests so you may have to resort to IL pretty tests.