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

rustbot has assigned @tgross35.
They will have a look at your PR within the next two weeks and either review your PR or reassign to another reviewer.

Use r? to explicitly pick a reviewer

[madhav-madhusoodanan]

I am tempted to perform a safety check here.
Is it a good idea to do such a check for the other unchecked_div and unchecked_rem implementations too?

Suggested change

	unsafe { intrinsics::unchecked_div(self, rhs) }
	if intrinsics::unlikely(rhs == 0 || ((self == Self::MIN) && (rhs == -1))) {
	self
	} else {
	// SAFETY: div by zero and by INT_MIN have been checked above
	unsafe { intrinsics::unchecked_div(self, rhs) }
	}