feat: swap endianness in-place in keccak implementation

[TomAFrench]

Description

Problem*

Resolves

Summary*

This PR removes the temp array created when swapping the endianness of the block_bytes array and just swaps the values in place. This removes some unnecessary reads/writes from brillig.

Additional Context

Documentation*

Check one:

• No documentation needed.
• Documentation included in this PR.
• [For Experimental Features] Documentation to be submitted in a separate PR.

PR Checklist*

• I have tested the changes locally.
• I have formatted the changes with Prettier and/or cargo fmt on default settings.