Update to 1.0 backend

[MilesCranmer]

This updates the backend to 1.0, which includes:

1. (BREAKING!) Change to file structure. Rather than hall_of_fame_{datestr}.csv, files are now stored under outputs/{datestr}_{hash}/hall_of_fame.csv which is cleaner and more extensible.
2. Creation of "Expression Specifications" which allow for the use of ParametricExpression and TemplateExpression.

TODO:

• Finish the implementation of complexity_mapping and add a unittest
• Fix remaining tests.
• Ensure automatic pushes to new URL.
• Unittests for ParametricExpression/TemplateExpression.
• Update hyperparameters.
• Update multithreading interface. (With nice deprecation warnings)

This will be released as a beta first, because there are a couple other changes to make (like updating default hyperparameters).

Still TODO:

• Add examples to documentation.
• Add autodiff_backend. Maybe just Zygote for now (?) as Enzyme hits some issues: Task switch error on Enzyme v0.13 EnzymeAD/Enzyme.jl#2081
• Logger integration

[coveralls]

Pull Request Test Coverage Report for Build 12100062277

Details

• 412 of 438 (94.06%) changed or added relevant lines in 13 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage decreased (-0.3%) to 93.389%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
pysr/julia_helpers.py	10	11	90.91%
pysr/init.py	4	6	66.67%
pysr/sr.py	216	239	90.38%

Files with Coverage Reduction	New Missed Lines	%
pysr/sr.py	1	92.87%

Totals
Change from base Build 11922443974:	-0.3%
Covered Lines:	1342
Relevant Lines:	1437

---

💛 - Coveralls