Add NonZero and NonMax types, generic over PrimitiveInt

Added

• Add wrapping_add and wrapping_sub functions (wznskrrp)
• Add NonZero struct to mirror core::num::NonZero, but made generic over PrimitiveInt (xooqvysu)
• Add NonMax struct to mirror the NonZero struct (msuozwwt)
  • Offers alternative to the nonmax crate.
  • Implemented in terms of NonZero type as stdlib doesn't offer it natively.

Changed

• Bump MSRV to 1.71