Log Message:
miller: update to 5.10.0.

ChangeLog:

Features:

- The unsparsify -f feature
- The new sort-within-records verb is an old ask, underway from the Go
  port, backported to C
- Likewise the truncate DSL function

Bugfixes:

- The count -n feature was not implemented as intended
- Pretty-print format now works correctly with --headerless-csv-output
- The seqgen verb now correctly tracks NR and FNR in the records it emits
- An intermittent JSON-parsing bug has been fixed