[DMN Designer] TextAreas can no longer be multi-line

TextAreaSingletonDOMElementFactory extends BaseSingletonDOMElementFactory that attaches a KeyDownHandlerCommon handler.

This handler intercepts KeyCodes.KEY_ENTER that flushes the content of the editor.

The KeyDownHandlerCommon handler should not respond to KeyCodes.KEY_ENTER for TextAreas.

Accetance criteria

User can put multiline for

• Literal expression
• Context
• Relation
• Invocation
• Function
• Decision Table