Remove locks in RadioButton and increase type safety (use generic types)

[h3xds1nz]

Description

Optimizes weird branching loops for cleanup, replace them with counting down loops instead.

• Replace _groupNameToElements Hashtable with Dictionary<string, List<WeakReference<RadioButton>>>.
• Use List<WeakReference<RadioButton>> instead of ArrayList to store weak references per group name.
• Use WeakReference<RadioButton> instead of untyped WeakReference.
• Initialize the List with at least 2 elements as we should expect more than 1 item per radio button group.
• Renamed _groupNameToElements to t_groupNameToElements as its ThreadStatic variable.
• I've also removed the locks on the collection as each Thread would gets its own copy anyways.
• Also we no longer walk the visual tree unless it is actually needed.

Customer Impact

Increased performance, cleaner codebase for developers.

Regression

No.

Testing

Local build, extensive testing with radio buttons.

Risk

Low to medium, I believe I've tested most of the edge cases as I was working on something with the build.

Microsoft Reviewers: Open in CodeFlow