[Feature Request] Add `stol` function

[YichengDWu]

Review Mojo's priorities

• [X] I have read the roadmap and priorities and I believe this request falls within the priorities.

What is your request?

atol is in the std but not stol, a similar function to strtol in C.

What is your motivation for this change?

More functionalities to parser strings.

Any other details?

No response