Adding test cases for idealized problems

[MaceKuailv]

There could be changes on the core code as well.

[codecov]

Codecov Report

Patch coverage: 72.88% and project coverage change: -0.53 ⚠️

Comparison is base (8d60702) 93.39% compared to head (391012d) 92.86%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #42      +/-   ##
==========================================
- Coverage   93.39%   92.86%   -0.53%     
==========================================
  Files          11       11              
  Lines        2604     2635      +31     
  Branches      711      718       +7     
==========================================
+ Hits         2432     2447      +15     
- Misses         72       84      +12     
- Partials      100      104       +4     

Impacted Files	Coverage Δ
seaduck/kernel_weight.py	95.16% <ø> (ø)
seaduck/ocedata.py	91.66% <33.33%> (-3.70%)	⬇️
seaduck/eulerian.py	93.95% <50.00%> (-0.30%)	⬇️
seaduck/lagrangian.py	95.70% <81.25%> (-1.16%)	⬇️
seaduck/topology.py	87.28% <100.00%> (+0.25%)	⬆️

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[MaceKuailv]

The doc build fail because it want to run in bubblebath environment hhhh. I will merge it, and try to fix it from my laptop.
codecov failed as usual. Nothing important is not tested. I am going to merge the changes.