Add script for converting ode2cellml

[finsberg]

Add script for converting .ode to .cellml and verify the round trip (e.g .ode -> .cellml -> .ode -> .cellml) produces the same files. Use myokit as adapter.

Also fix and issue with float values becoming evaluated by sympy for example the expression

(v - 4.823)/51.12

will silently be turned into

0.0195618153364632*v - 0.0943466353677621

Now, the full expression is carried through the code generation which will hopefully improve the precision

[codspeed-hq]

Merging this PR will not alter performance

✅ 8 untouched benchmarks

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_{Comparing ode2cellml (5b01107) with main (0f69a2d)}