RadioButton: No FormControl support

[ilhan007]

Created the issue on behalf of SAP Build Process Automation:
RadioButton - FormControl support is missing.

Expected Behavior

Steps to Reproduce

1. Go to '...'
2. ...
3. ...

Isolated Example

Context

• UI5 Web Components version: {...}
• UI5 Web Components for Angular version: {...}
• Angular Version: {...}
• OS/Platform: {...}
• Browser: {...}
• Affected component: {...}

Log Output / Stack Trace / Screenshots

{...}

Priority

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• Medium
• High
• Very High

The priority indicates the severity of the issue. To set the appropriate priority consider the following criteria:

• Breaks entire application or system - High or Very High
• Accessibility issue - Medium or High
• Functional issue - Medium or High
• Visual issue - Low or Medium

Note: The priority might be re-evaluated by the issue processor.

Stakeholder Info (if applicable)

• Organization: {...}
• Business impact: {...}

[timogeib]

Please check the CODE example in
https://sap.github.io/ui5-webcomponents/playground/?path=/docs/main-radio-button--docs
ui5-radio-button are nested, Option 2 is there multiple times.
Added example to https://github.tools.sap/I555913/ui5-webcomponents-sandbox for issue 94
FormControl value is set to "true" as soon as a radio is selected, not the selected option. Default form FormControl is not set.