backend: Integrate fix for ISO value scaling in dataset metadata

[ethanjli]

This PR fixes #524 by integrating PlanktoScope/device-backend#77 into the master branch for the v2025.0.0 release cycle.

Manual test instructions:

• Acquire various test datasets with a few different ISO settings. Check the metadata.json files of the resulting datasets to confirm that the values of their acq_camera_iso field exactly match the actual ISO settings used.

  Note that certain other metadata fields should be missing or invalid if frontend: Fix the dashboard's metadata-saving regression #550 has not yet been integrated into this PR (e.g. via merging into the master branch). For example, acq_imaged_volume will probably be NaN here.

TODOs:

• (Ethan) Test the resulting adafruithat OS image (bookworm-based)
• (Sonny) Test the resulting planktoscopehat OS image (bookworm-based)

[ethanjli]

Note: #560 has now integrated the code change made by this PR, so now this PR is basically just a CHANGELOG.md update. I'm still going to wait for testing feedback from @sonnyp before I merge this PR, just in case further code changes/fixes are needed for planktoscopehat.

[ethanjli]

As discussed in the 2024-04-09 core team meeting, we'll have Sonny test this PR after merging, as part of testing of the v2025.0.0-alpha.0 prerelease. So I'll merge this PR now.