fix: compare nodespecs based on ngpu/ncpu/mem first, before price

[mortenpi]

The documentation says that nodespec returns the smallest node, not necessarily the cheapest. This fixes the behavior where nodespec (and therefore submit_job) would pick the wrong node if there is a bigger, but cheaper one available, and clarifies the documentation.

It also makes the output for nodespecs() sorted, but that's an implementation detail, and hence not documented.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 40.61%. Comparing base (6799ba1) to head (1964bbf).

Additional details and impacted files

@@             Coverage Diff             @@
##             main      #49       +/-   ##
===========================================
- Coverage   78.65%   40.61%   -38.05%     
===========================================
  Files          16       16               
  Lines        2244     2221       -23     
===========================================
- Hits         1765      902      -863     
- Misses        479     1319      +840     

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[pfitzseb]

1.6 failure seems spurious?

[mortenpi]

1.6 failure seems spurious?

Yep. I missed the doctest failures though.