Introduce the Zero trait

[bitzoic]

Description

Introduces the Zero trait with the following functions to be implemented:

• zero()
• is_zero()

This falls inline with what we see in Rust's Zero Trait, making the language feel and look more like Rust.

This PR also deprecates the following:

• ZERO_B256 -> b256::zero()
• ZERO_U256 -> u256::zero()

To define a u256 or b256 zero address, the following should be used:

let zero_b256 = b256::zero();
let zero_u256 = u256::zero();

A common use of the ZERO_B256 was to define the zero addresses and contract id`:

let zero_address = Address::from(ZERO_B256);
let zero_contract = ContractId::from(ZERO_B25);

The following is now possible:

let zero_address = Address::zero();
let zero_contract = ContractId::zero();

The following types now implement the Zero trait:

• u8
• u16
• u32
• u64
• u256
• b256
• SubId
• AssetId
• ContractId
• Address
• EvmAddress
• U128
• B512

Closes #5830

Checklist

• I have linked to any relevant issues.
• I have commented my code, particularly in hard-to-understand areas.
• I have updated the documentation where relevant (API docs, the reference, and the Sway book).
  • If my change requires substantial documentation changes, I have requested support from the DevRel team
• I have added tests that prove my fix is effective or that my feature works.
• I have added (or requested a maintainer to add) the necessary Breaking* or New Feature labels where relevant.
• I have done my best to ensure that my PR adheres to the Fuel Labs Code Review Standards.
• I have requested a review from the relevant team or maintainers.

[IGI-111]

I know Rust's num has it, but is it common enough to want to condition things over the ability to produce a identity element? These could just be part of their respective impls and the trait be a library.

As in Rust, incidentally.