Add non-panicking variants of pow for Integers

[milesand]

std (and core) does not include non-panicking variants of pow. As we already have such variants of other possibly-overflowing operations in the std, it may be a good idea to add such functionality for symmetry.

[sfackler]

It seems reasonable to take a PR adding checked_pow!

[frewsxcv]

relevant issue and pr:

• Tracking issue for non-panicking pow #48320
• Add non-panicking variants of pow for integer types #48321