chore: update main to v16

[mpoke]

Description

Closes: NA

• replace gaia/v15 with gaia/v16
• update test.yml
• add v16 update handler

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Author Checklist

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I have...

• Included the correct type prefix in the PR title
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• Provided a link to the relevant issue or specification
• Reviewed "Files changed" and left comments if necessary
• Confirmed all CI checks have passed

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• Confirmed the correct type prefix in the PR title
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• Confirmed that this PR does not change production code

[MSalopek]

LGTM!