Fixes #75147 (VB) and the related C# issue

Problem

SemanticModel.GetTypeInfo() was returning null Type when called on the Type property of an ObjectCreationExpressionSyntax, even though GetSymbolInfo() correctly returned the type symbol:

var objCreation = (ObjectCreationExpressionSyntax)...;
var typeInfo = semanticModel.GetTypeInfo(objCreation.Type);
// typeInfo.Type was null (unexpected)
var symbolInfo = semanticModel.GetSymbolInfo(objCreation.Type);
// symbolInfo.Symbol was correctly populated

This behavior was inconsistent - the Type node is in a "type-only context" (confirmed by SyntaxFacts.IsInTypeOnlyContext returning true), and other type-only contexts correctly return type information.

Solution

C# Changes

Removed the explicit check in CSharpSemanticModel.GetTypeInfoForNode() that was blocking type information from being returned for ObjectCreationExpressionSyntax.Type nodes. The check dates back to the early days of Roslyn but there was no clear reason for this restriction.

Visual Basic Changes

1. Removed the equivalent blocking check in SemanticModel.GetTypeInfoForNode()
2. Added special handling in CanGetSemanticInfo() to allow semantic information retrieval for the Type node of ObjectCreationExpression even when marked as IsMissing
   • VB's syntax tree marks simple identifier types (e.g., New MyClass()) as IsMissing, while qualified types (e.g., New N.MyClass()) are not marked as missing
   • This is a quirk of VB's syntax tree construction, and the special case ensures both work correctly

Testing

• Added comprehensive tests for both C# and VB covering simple types, generic types, and qualified names
• Updated existing VB tests that were expecting the old null behavior
• All existing compiler tests pass (19,250+ C# semantic tests, all VB semantic tests)

Fixes #78783

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