Capitalize and Uncapitalized are implemented multiple times

[chwoerz]

Acknowledgement

• [x] I acknowledge that issues using this template may be closed without further explanation at the maintainer's discretion.

Comment

The intrinsic type implementation for Capitalize and Uncapitalize are implemented multiple times in the checker.ts. They should be moved into a reusable function.

https://github.com/microsoft/TypeScript/issues/60206