chore: merge release/v1.28.0 / v1.28.0-rc4 back to master

[rjan90]

During the prep of shipping Lotus v1.28.0-rc2/rc3/rc4 we added the Calibration network upgrade epoch, but we did not land this change in master.

Proposed Changes

• Merge release/v1.28.0 branch back into master.
• Update version to v1.28.1-dev in master.

Checklist

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