Added unchecked_div and unchecked_rem to signed and unsigned numerical types

[madhav-madhusoodanan]

Context

Adds unchecked_div and unchecked_rem to signed and unsigned numerical types in core.
This is an unstable addition.

Related Issue

• Tracking Issue for unchecked_div_rem #136716

[rustbot]

r? @tgross35

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[tgross35]

r? @the8472 since you expressed some concerns at #136716

[the8472]

On the tracking issue I was mostly voicing conern about the naming, i.e. having two functions with the same name but different safety preconditions.
The libs-API team already accepted this as unstable addition so my concern shouldn't be a blocker for this PR, but I'd want to be reconsidered before stabilization, that's why I noted it on the tracking issue.

[Sky9x]

Some of the requested changes are only on 1 of the functions, please make sure they are applied to all 4 (if applicable).

[madhav-madhusoodanan]

Have updated documentation and corrected the failure condition being passed to assert_unsafe_precondition for unchecked_div and unchecked_rem functions in int_macros.rs.

Special thanks to @Sky9x for the suggestions.

@rustbot review

[Sky9x]

LGTM!
Tip: You can collapse review comments by clicking on "Resolve Conversation" once you've addressed it

[madhav-madhusoodanan]

I would be grateful if you could please take a look at this PR @the8472.

[karolzwolak]

@the8472 friendly ping from wg-triage to review this