Addressing CR feedback:
New SyntaxKind.BindingElement
Introduced new VariableLikeDeclaration and BindingElement types
Cleaned up VariableDeclaration, ParameterDeclaration, PropertyDeclaration types
Node kind of binding element is always SyntaxKind.BindingElement
Changed CheckVariableDeclaration to CheckVariableLikeDeclaration
Reorganized CheckVariableLikeDeclaration