FieldTypeMacro constructor Null safety

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

FieldTypeMacro class

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