Rollup merge of #82683 - jturner314:int-div-rem-doc-panic, r=nikomatsakis

Rollup merge of #82683 - jturner314:int-div-rem-doc-panic, r=nikomatsakis

Document panicking cases for integer division and remainder

This PR documents the cases when integer division and remainder operations panic. These operations panic in two cases: division by zero and overflow.

It's surprising that these operations always panic on overflow, unlike most other arithmetic operations, which panic on overflow only when `debug_assertions` is enabled. The panic on overflow for the remainder is also surprising because a return value of `0` would be reasonable in this case. ("Overflow" occurs only for `MIN % -1`.) Since the panics on overflow are somewhat surprising, they should be documented.

I guess it's worth asking: is panic on overflow (even when `debug_assertions` is disabled) the intended behavior? If not, what's the best way forward?