Keep generic defaults for method types

[elycruz]

According to Ts Generic Parameter Defaults doc there doesn't seem to be any inherent performance/flexibility downsides to set defaults for method generic types (where it makes sense).

For now, will keep generics defaults on method types to ensure maximum flexibility of changes for Fjl-v2.0.

Acceptance Criteria

• Keep generic defaults, where they make sense, for method types:

Keep the defaults for:

• Method "type" declarations - Ensures the [method] types stay flexible.
• For methods that take multiple generics and have one or more of those generics take one the defined generics as a generic (think 'map' fn operation, etc.), in these cases it makes sense to have defaults as to make the methods easier to use.

Reference:

https://www.typescriptlang.org/docs/handbook/2/generics.html#generic-parameter-defaults