fix: clear ModelOutput fields via mapping to free tensors

[AngeloDanducci]

Pull Request

Issue

Fixes #1549

Description

HuggingFace backend now properly frees tensors when nulling fields.

Testing

• Tests added to the respective file if code was changed
• New code has 100% coverage if code was added
• Ensure existing tests and github automation passes (a maintainer will kick off the github automation when the rest of the PR is populated)

Attribution

• AI coding assistants used

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[jakelorocco]

@AngeloDanducci thanks for picking up the issue. I think the initial PR that spotted the issue in the generate from raw path might actually be fixing it in the chat path as well? #1518

[AngeloDanducci]

@jakelorocco yep looks like it's covered there, I will update the PR to auto close 1549 and close this PR.

[jakelorocco]

Thank you; sorry for the duplicate work, I didn't realize the other PR was going to handle it when I opened the issue and didn't realize the duplication till after I saw your PR.

[AngeloDanducci]

No worries - the nature of being proactive sometimes.