Add PEtab math parser and sympy converter

[dweindl]

Related to https://github.com/PEtab-dev/PEtab/pull/579

• ANTLR grammar for PEtab math expressions + derived lexer/parser/visitor
• Test cases
• PEtab -> SymPy converter

Note: All sympy symbols in PEtab match expressions now have real=True.

[dweindl]

• [x] move test cases to https://github.com/PEtab-dev/petab_test_suite
• [x] Tests for implicit bool<->float conversion?
• [x] Implement implicit bool<->float conversion?

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 74.28256% with 233 lines in your changes missing coverage. Please review.

Project coverage is 75.68%. Comparing base (41481bb) to head (18c59e4).

Files	Patch %	Lines
petab/math/_generated/PetabMathExprParser.py	73.06%	140 Missing and 34 partials :warning:
petab/math/SympyVisitor.py	69.23%	19 Missing and 21 partials :warning:
...etab/math/_generated/PetabMathExprParserVisitor.py	61.36%	16 Missing and 1 partial :warning:
petab/math/_generated/PetabMathExprLexer.py	96.00%	1 Missing and 1 partial :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #260 +/- ## =========================================== - Coverage 76.12% 75.68% -0.45% =========================================== Files 36 40 +4 Lines 3238 4137 +899 Branches 785 891 +106 =========================================== + Hits 2465 3131 +666 - Misses 568 744 +176 - Partials 205 262 +57 ```

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[dweindl]

I didn't check _generated much.

Good. That's auto-generated and not really meant to be read.