chore: remove some 'nonrec'

[kim-em]

nonrec is nearly always obfuscatory: it tells the reader "this apparent recursive call is not actually, but I'm going to leave you to guess what it is instead", when we could just disambiguate and tell the reader.

However I'm not sure I have the patience to go through the remaining 600 uses. (A few are genuinely useful, but I guess less than 10%.)

[kim-em]

There is occasionally a performance gain from using nonrec, but I think in any place where we want to take advantage of this we should explicitly comment to that effect.

[github-actions]

PR summary a9e65f796c

Import changes for modified files

No significant changes to the import graph

Import changes for all files

Files	Import difference

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Declarations diff

No declarations were harmed in the making of this PR! 🐙

You can run this locally as follows

## summary with just the declaration names:
./scripts/declarations_diff.sh <optional_commit>

## more verbose report:
./scripts/declarations_diff.sh long <optional_commit>

The doc-module for script/declarations_diff.sh contains some details about this script.

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No changes to technical debt.

You can run this locally as

./scripts/technical-debt-metrics.sh pr_summary

• The relative value is the weighted sum of the differences with weight given by the inverse of the current value of the statistic.
• The absolute value is the relative value divided by the total sum of the inverses of the current values (i.e. the weighted average of the differences).