Fixes for Open Boundary Systems for free surfaces

[svchb]

Depends on #610
Depends on #608
Depends on #606
Depends on #605
Depends on #603
Depends on #599

[codecov]

Codecov Report

Attention: Patch coverage is 66.66667% with 10 lines in your changes missing coverage. Please review.

Project coverage is 69.34%. Comparing base (eb9f41b) to head (cde7990).

Files with missing lines	Patch %	Lines
...oundary/open_boundary/method_of_characteristics.jl	44.44%	5 Missing ⚠️
src/schemes/boundary/open_boundary/system.jl	69.23%	4 Missing ⚠️
...c/schemes/boundary/open_boundary/boundary_zones.jl	75.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #609      +/-   ##
==========================================
- Coverage   69.37%   69.34%   -0.04%     
==========================================
  Files          85       85              
  Lines        5124     5141      +17     
==========================================
+ Hits         3555     3565      +10     
- Misses       1569     1576       +7     

Flag	Coverage Δ
unit	69.34% <66.66%> (-0.04%)	⬇️

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[svchb]

Note there were other things in this PR most have been reverted since it is was not leading anywhere. Or it was conflicting with #623