Add VB new features (#44636)

* Add VB new features

- Fixes #44190:  Add note that Visual Basic can consume types (defined in C#) that specify the `unmanaged` constraint.
- Fixes #44174: VB Overload resolution respects the OverloadResolutionPriorityAttribute.

In these changes, I made the necessary updates for accuracy with the current compiler. Then, I did an edit for style and updated per style.

You may want to review the two commits separately to see the semantic changes distinct from the grammar and style changes.

* edit and freshness pass

* word choice

* Apply suggestions from code review

Co-authored-by: Genevieve Warren <[email protected]>

* rework paragraph on `unmanaged`

Try to make this restriction more clear.

* Update docs/visual-basic/programming-guide/language-features/data-types/generic-types.md

Co-authored-by: Genevieve Warren <[email protected]>

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Co-authored-by: Genevieve Warren <[email protected]>

Author: BillWagner