DeclarationMacro constructor Null safety

1. macro_builder
2. definition
3. DeclarationMacro
4. DeclarationMacro constructor

DeclarationMacro class

1. Constructors
2. DeclarationMacro
3. Properties
4. hashCode
5. runtimeType
6. Methods
7. noSuchMethod
8. toString
9. Operators
10. operator ==