feat(num): improve error messages for TryFromIntError

[sorairolake]

• Tracking issue: Tracking Issue for try_from_int_error_kind #153978

This pull request improves the Display trait implementation for TryFromIntError by providing more specific error messages based on the underlying IntErrorKind.

Currently, the error message is always "out of range integral type conversion attempted". This makes debugging difficult because users cannot distinguish the detailed cause of the error from the error message.

IntErrorKind::Empty and IntErrorKind::InvalidDigit should be unreachable.

I don't think this is breaking changes, because similar changes were made in the past in #96168.

See also: https://users.rust-lang.org/t/are-changes-to-fmt-display-considered-breaking/59775

[rustbot]

r? @Mark-Simulacrum

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[sorairolake]

@rustbot label +T-libs-api -T-libs
r? libs-api