maint: Remove usage of `folly::enumerate`

[jjerphan]

Reference Issues/PRs

What does this implement or fix?

Any other comments?

Checklist

Checklist for code changes...

• [ ] Have you updated the relevant docstrings, documentation and copyright notice?
• [ ] Is this contribution tested against all ArcticDB's features?
• [ ] Do all exceptions introduced raise appropriate error messages?
• [ ] Are API changes highlighted in the PR description?
• [ ] Is the PR labelled as enhancement or bug so it appears in autogenerated release notes?

[willdealtry]

This is a very trivial class to implement. Might it not be better to just have our own version rather than making such significant changes across the codebase? https://github.com/man-group/ArcticDB/pull/1386

We can credit folly with the original implementation, but there's really not much to it, and not really many other ways to do accomplish it, and it does add significant clarity to the code in certain circumstances

[jjerphan]

This is a very trivial class to implement. Might it not be better to just have our own version rather than making such significant changes across the codebase? https://github.com/man-group/ArcticDB/pull/1386

Yes, definitely (this PR is still a draft and I switched to some other tasks). I was just trying to see if a simple entire removal of the header was possible, but we definitely need to add some syntactic sugar as proposed by #1386.

[jjerphan]

Closing for now, might reopen one day.