feat(string family): implement cl.throttle

[zetanumbers]

Solves #270

• Port all of the tests;
• Integer overflow safety.

[zetanumbers]

I did not add any new integer overflow checks, but i think they should be.

[zetanumbers]

I think i've applied all the suggestions. Tell me what should i also do.

[romange]

Thanks, much better. Have a few minor comments.
I think after the next pass, we will submit it.

[romange]

Please use pre-commit checks to verify formatting.
See here on how to install them: https://github.com/dragonflydb/dragonfly/blob/main/CONTRIBUTING.md#before-you-make-your-changes

[romange]

Thanks again for contributing this feature, @zetanumbers !

[zetanumbers]

Thank you for helping me figure out how to do it.