Remove/deprecate legacy Solution handling

[ischoegl]

Changes proposed in this pull request

Removal of legacy MATLAB toolbox #1670 allows for some simplifications / deprecations:

• Remove remaining legacy wall methods from CAPI and C++
• Deprecate setThermoMgr/setKineticsMgr for 0D
• Move deprecation warning for empty reactor objects from Python to C++

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

Partially addresses #1457

_A clean resolution of #1457 will require pushing the Python _WeakrefProxy approach to the C++ layer?_

Checklist

• [x] The pull request includes a clear description of this code change
• [x] Commit messages have short titles and reference relevant issues
• [x] Build passes (scons build & scons test) and unit tests address code coverage
• [x] Style & formatting of contributed code follows contributing guidelines
• [x] The pull request is ready for review

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 88.09524% with 5 lines in your changes are missing coverage. Please review.

Project coverage is 72.80%. Comparing base (ed27faf) to head (a8aae47). Report is 1 commits behind head on main.

:exclamation: Current head a8aae47 differs from pull request most recent head 3f20538. Consider uploading reports for the commit 3f20538 to get more accurate results

Files	Patch %	Lines
include/cantera/zeroD/ReactorBase.h	50.00%	0 Missing and 1 partial :warning:
src/zeroD/IdealGasConstPressureMoleReactor.cpp	66.66%	1 Missing :warning:
src/zeroD/IdealGasConstPressureReactor.cpp	66.66%	1 Missing :warning:
src/zeroD/IdealGasMoleReactor.cpp	66.66%	1 Missing :warning:
src/zeroD/IdealGasReactor.cpp	66.66%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1685 +/- ## ========================================== + Coverage 72.76% 72.80% +0.04% ========================================== Files 378 378 Lines 56986 56956 -30 Branches 20691 20679 -12 ========================================== + Hits 41468 41469 +1 + Misses 12463 12434 -29 + Partials 3055 3053 -2 ```

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[ischoegl]

Ready for review ... decided to restrict this PR to Reactor cleanup that became possible after the removal of the legacy MATLAB toolbox.

[ischoegl]

@speth - thank you for your feedback. I believe I started some confusion with a deprecation warning that incorrectly implied that something was introduced in Cantera 3.0, while only being implemented after its release (non-empty Reactors). I updated/corrected the warnings, which should take care of your concerns.

Regarding changes to the reactor content after instantiation, we can definitely think about removing this capability, but either insert or setSolution are needed until the deprecation cycle is complete. I agree that any changes should be discussed in a separate PR.