feat(stdlib): Make Hasher trait generic over input type

[crStiv]

Makes the Hasher trait generic with type parameter T to support different input types beyond Field. This change:

• Adds type parameter T to Hasher trait
• Updates BuildHasher and BuildHasherDefault accordingly
• Maintains backwards compatibility with existing Field implementations
• Removes TODO comment about generic types

[github-actions]

Thank you for your contribution to the Noir language.

Please do not force push to this branch after the Noir team have started review of this PR. Doing so will only delay us merging your PR as we will need to start the review process from scratch.

Thanks for your understanding.

[TomAFrench]

This is missing necessary trait bounds. Will review later.