Make various small fixes for Fulu code

[jtraglia]

PR Description

• In strings, change several instances of "FULU" to "Fulu"
  • This is more consistent with other forks.
• Rename throttling-dataColumn to throttling-columns
  • It should have been plural to match other keys.
  • Can rename to dataColumns if desired.
• Add missing length check for blobsCellBundle.getProofs() in builder flow.
  • We checked this in Deneb, should probably check here too.
• Rename blobSidecarsAvailabilityDeprecationSlot to blobSidecarsDeprecationSlot.
  • I found this function name to be misleading. I thought you were going to drop blobs at this slot.
• Remove an unused parameter in computeDataColumnSidecarBackboneSubnets.
  • Did you intend to use this?

Documentation

• I thought about documentation and added the doc-change-required label to this PR if updates are required.

Changelog

• I thought about adding a changelog entry, and added one if I deemed necessary.

[jtraglia]

Hmm I added @SuppressWarnings("UnusedVariable") to NodeIdToDataColumnSidecarSubnetsCalculator#createAtSlot because I didn't want to do a large refactor there. I don't really understand why this needs to be for a specific slot.

[tbenr]

I think this stuff should be exposed via SpecLogic and we should remove those "if milestone is fulu".
But this can be for another PR