Refactor Py2NRNString.

[1uc]

The Py2NRNString consisted of (what's now) a unique_cstr. The ctor would create the cstr, and {g,s}et_pyerr were non-static methods. They needed to check if the cstr as a nullptr, but where only ever called after checking that it was a nullptr.

This commit separates several notions:

• Ownership is handled by unique_cstr.
• An ASCII string is extracted from a Python object using as_ascii.
• Both {g,s}et_pyerr were made static an are independent of each other and from converting a Python object to an (ASCII) C-string.
• The PyErr2NRNString was removed.

[azure-pipelines]

✔️ 9d6872b -> Azure artifacts URL

[azure-pipelines]

✔️ c6523a2 -> Azure artifacts URL

[codecov]

Codecov Report

Attention: Patch coverage is 87.69231% with 8 lines in your changes missing coverage. Please review.

Project coverage is 67.07%. Comparing base (925a225) to head (fe213e8).

Files with missing lines	Patch %	Lines
src/nrnpython/nrnpy_utils.cpp	83.33%	3 Missing ⚠️
src/nrnpython/inithoc.cpp	0.00%	2 Missing ⚠️
src/nrnpython/nrnpy_hoc.cpp	90.00%	2 Missing ⚠️
src/nrnpython/nrnpy_p2h.cpp	75.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3249      +/-   ##
==========================================
- Coverage   67.08%   67.07%   -0.01%     
==========================================
  Files         571      571              
  Lines      111092   111052      -40     
==========================================
- Hits        74523    74487      -36     
+ Misses      36569    36565       -4     

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[azure-pipelines]

✔️ fe213e8 -> Azure artifacts URL

[bbpbuildbot]

Logfiles from GitLab pipeline #239451 (:white_check_mark:) have been uploaded here!

Status and direct links:

• ✅ mac_m1_cmake_build: [cmake, ON, OFF, OFF, address]
• ✅ spack_setup
• ✅ build:nmodl
• ✅ build:neuron:nmodl:intel:legacy
• ✅ build:neuron:nmodl:intel:shared
• ✅ build:neuron:nmodl:nvhpc:acc:legacy
• ✅ build:neuron:nmodl:nvhpc:acc:shared
• ✅ build:neuron:nmodl:nvhpc:omp:legacy
• ✅ build:neuron:nmodl:nvhpc:omp
• ✅ test:neuron:nmodl:intel:legacy
• ✅ test:neuron:nmodl:intel:shared
• ✅ test:neuron:nmodl:nvhpc:acc:legacy
• ✅ test:neuron:nmodl:nvhpc:acc:shared
• ✅ test:neuron:nmodl:nvhpc:omp:legacy
• ✅ test:neuron:nmodl:nvhpc:omp

[sonarcloud]

Quality Gate passed

Issues
11 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud