## Description

Introduces the following functions to be implemented:
- `zero()`
- `is_zero()`

This falls inline with what we see in [Rust's Zero
Trait](https://docs.rs/num/latest/num/traits/trait.Zero.html), 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:

```sway
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`:
```sway
let zero_address = Address::from(ZERO_B256);
let zero_contract = ContractId::from(ZERO_B25);
```
The following is now possible:
```sway
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

- [x] I have linked to any relevant issues.
- [x] I have commented my code, particularly in hard-to-understand
areas.
- [x] 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](https://github.com/FuelLabs/devrel-requests/issues/new/choose)
- [x] I have added tests that prove my fix is effective or that my
feature works.
- [x] I have added (or requested a maintainer to add) the necessary
`Breaking*` or `New Feature` labels where relevant.
- [x] I have done my best to ensure that my PR adheres to [the Fuel Labs
Code Review
Standards](https://github.com/FuelLabs/rfcs/blob/master/text/code-standards/external-contributors.md).
- [x] I have requested a review from the relevant team or maintainers.

---------

Co-authored-by: K1-R1 <77465250+K1-R1@users.noreply.github.com>