Support the newest OPeNDAP version of Caravan, patch data issues.

[BSchilperoort]

This PR fixes some issues in the already hosted dataset:

• homogenizes variable names
• converts all units
• massages the data into the right format to have the data the users needed

It also adds a new kwarg to download the shapefiles, by default downloading the shapefile is now skipped.

[BSchilperoort]

@RolfHut could you try this branch to see if it fits with what you started in #433

[codecov]

Codecov Report

❌ Patch coverage is 55.35714% with 25 lines in your changes missing coverage. Please review.
✅ Project coverage is 78.10%. Comparing base (2f2d7c0) to head (9edf8dd).
⚠️ Report is 11 commits behind head on main.

Files with missing lines	Patch %	Lines
src/ewatercycle/_forcings/caravan.py	53.70%	17 Missing and 8 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #458      +/-   ##
==========================================
- Coverage   78.83%   78.10%   -0.74%     
==========================================
  Files          28       29       +1     
  Lines        1810     1850      +40     
  Branches      218      224       +6     
==========================================
+ Hits         1427     1445      +18     
- Misses        325      342      +17     
- Partials       58       63       +5     

Files with missing lines	Coverage Δ
src/ewatercycle/_forcings/_caravan_reference.py	100.00% <100.00%> (ø)
src/ewatercycle/_forcings/caravan.py	71.42% <53.70%> (-11.73%)	⬇️

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