Some fixes for IonFlame issues

[ischoegl]

Changes proposed in this pull request

• Apply band-aid fix to ion_burner_flame.py - a reduction of domain size makes the example more stable; there is no apparent reason for simulations to fail on a larger domain, which points at underlying issues that should be fixed at a later point cherry-picked to Fix examples #905
• Fix ch4_ion.yaml that did not match ch4_ion.cti cherry-picked to Fix examples #905
• Fix apparent glitch that results in the Poisson solver not being activated (Edit: the fix has no effect as it affects C++ code that is not used)
• Remove upstream von Neumann boundary condition for ionized species (see also Electron #700)
• Add optional plots to IonFlow-based examples
• Fix export of _other columns from IonFlow (i.e. grid, etc.) cherry-picked to Fix examples #905

Additional issues that surfaced while reviewing code are listed in #913 - changes are more extensive and should be handled by a separate PR (potentially after the release of 2.5).

PS: After cherry-picking 3 fixes into #905, the remaining changes are not worth keeping this PR open.

If applicable, fill in the issue number this pull request is fixing

Fixes #909

Checklist

• There is a clear use-case for this code change
• The commit message has a short title & references relevant issues
• Build passes (scons build & scons test) and unit tests address code coverage
• The pull request is ready for review

[ischoegl]

@BangShiuh ... could you have a brief look at this (and the corresponding bug report in #911)?

[codecov]

Codecov Report

Merging #912 into main will increase coverage by 0.02%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main     #912      +/-   ##
==========================================
+ Coverage   71.19%   71.21%   +0.02%     
==========================================
  Files         376      376              
  Lines       46211    46199      -12     
==========================================
+ Hits        32898    32900       +2     
+ Misses      13313    13299      -14     

Impacted Files	Coverage Δ
src/oneD/IonFlow.cpp	74.46% <ø> (+9.43%)	⬆️
src/base/AnyMap.cpp	83.99% <0.00%> (-0.05%)	⬇️
test/general/test_containers.cpp	99.57% <0.00%> (-0.02%)	⬇️

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[ischoegl]

On further inspection, the Python attribute electric_field_enabled (as well as the C++ counterparts) has no effect on the actual solution - the implementation is incomplete as the C++ vector m_do_electric_field is set but never used. Edit: this behavior is now reported as part of #913 - I am not planning to address it here.

[ischoegl]

@bryanwweber ... I added plots to the examples, and fixed another glitch for the SolutionArray export of IonFlow. At this point, I think this PR ready for review.

[ischoegl]

After cherry-picking 3 fixes into #905, the remaining changes are not worth keeping this PR open.