Update to forc v0.60.0

[bitzoic]

Type of change

• Improvement (refactoring, restructuring repository, cleaning tech debt, ...)

Changes

The following changes have been made:

• Updates the repository to use forc v0.60.0
• Makes fields in signed integers and fixed point numbers private
• Adds Self::zero(), self::is_zero(), and self::underlying() to signed integers and fixed point numbers

Breaking Changes

Public struct fields are now PRIVATE in the fixed_point and signed_integers libraries. If the fields are needed, they can be fetched with a corresponding my_type.underlying() function. For example, I8's underlying u8 may be fetched with:

let my_i8: I8 = I8::zero();
let underlying: u8 = my_i8.underlying();

For types that have a non_negative field, the same applies:

let my_ifp64: IFP64 = IFP64::zero();
let non_negative: bool = my_ifp64.non_negative();

[bitzoic]

Dependent on FuelLabs/sway-standards#96