Extract FERC Form 60 DBF data to SQLite

[e-belfer]

Addresses the last bit of issue #1984, by adding FERC Form 60 DBF data as a .sqlite database following the template for FERC Form 6.

To do:

• update release notes
• poke at the guts and make sure things look as expected

PR Checklist

• Merge the most recent version of the branch you are merging into (probably dev).
• All CI checks are passing. Run tests locally to debug failures
• Make sure you've included good docstrings.
• Update the release notes and reference reference the PR and related issues.
• Do your own explanatory review of the PR to help the reviewer understand what's going on and identify issues preemptively.

[codecov]

Codecov Report

Patch coverage: 100.0% and no project coverage change.

Comparison is base (ffffedc) 88.4% compared to head (2031b5c) 88.4%.

Additional details and impacted files

@@          Coverage Diff          @@
##             dev   #2734   +/-   ##
=====================================
  Coverage   88.4%   88.4%           
=====================================
  Files         88      89    +1     
  Lines      10176   10199   +23     
=====================================
+ Hits        9001    9024   +23     
  Misses      1175    1175           

Impacted Files	Coverage Δ
src/pudl/extract/ferc6.py	100.0% <ø> (ø)
src/pudl/metadata/sources.py	100.0% <ø> (ø)
src/pudl/extract/ferc.py	100.0% <100.0%> (ø)
src/pudl/extract/ferc60.py	100.0% <100.0%> (ø)
src/pudl/settings.py	98.8% <100.0%> (+<0.1%)	⬆️

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[zaneselvans]

Looks like it extracted the FERC Form 60 DBF data!

[e-belfer]

f60_admin and f60_s0_checks and f60_s0_row_changes are empty, as expected. Everything else looks good.