Add abstract TSHasOptionalTypeParameterInstantiation base type.
Add abstract TSHasOptionalTypeParameterInstantiation base type.

Inspired by @bnjmnt4n's comment here:
https://github.com/benjamn/ast-types/pull/309#issuecomment-461083326

benjamn/ast-types,benjamn/ast-types,benjamn/ast-types