Implement Hash trait for Bytes and String types

[bitzoic]

Description

The current Hasher implementation uses the sha256() and keccak256() functions provided in the Bytes type implementation.

This PR moves the assembly block that does the hashing into the Hasher. This allows for the homogenous syntax of hashing any type and moves all hashing into the hash.sw file.
This PR also implements the Hash trait for the Bytes and String types.

Before:

assert(sha256(my_string) == my_bytes.sha256());

After:

assert(sha256(my_string) == sha256(my_bytes));

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).
• 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.

[esdrubal]

LGTM!