fix: show methods for `ComputeConfig` and `NodeSpec`

[mortenpi]

The oneliner show/repr methods were outdated. This adds tests that actually parse the output, making sure we recover the original object.

[codecov-commenter]

Codecov Report

Merging #34 (131d2d4) into main (91a7664) will decrease coverage by 54.84%. The diff coverage is 12.50%.

@@             Coverage Diff             @@
##             main      #34       +/-   ##
===========================================
- Coverage   76.49%   21.66%   -54.84%     
===========================================
  Files          16       16               
  Lines        2187     2165       -22     
===========================================
- Hits         1673      469     -1204     
- Misses        514     1696     +1182     

Files	Coverage Δ
src/node.jl	85.50% <100.00%> (-7.25%)	:arrow_down:
src/jobsubmission.jl	1.49% <0.00%> (-82.27%)	:arrow_down:

... and 12 files with indirect coverage changes

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