Adding _ch to channel tag and _pl to planet tag in S5 variable names

[taylorbell57]

This PR reformats the fitted variable names in Stage 5 to use _ch# for different channels and _pl# for different planets. This will make the code far more robust since we can far more easily identify the channel and planet number, and this should also help with Stage 6 bugs. It will also make the variable names a bit more human readable, and this PR should also fix multiple bugs related to trying to manually set different priors or fixed values for different channels.

These changes resolve #643

While I was at it, I also added support for ecosw and esinw in astrophysical models which avoids the well known ecc>0 bias of fitting for ecc and w directly.

I still need to fully integrate and test the _pl tags, especially for starry, and I still need to do a bunch of testing. For now I'm just opening a draft PR to help me keep track of my progress, so don't worry about reviewing it until I mark it as ready for review.

Note, this change is going to break backwards compatibility for S6 running on old S5 outputs, but that isn't a huge deal since S6 isn't critical and we're working towards v1.0

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 38.50267% with 345 lines in your changes missing coverage. Please review.

Project coverage is 54.01%. Comparing base (a939236) to head (caf5823).

Files	Patch %	Lines
src/eureka/S6_planet_spectra/s6_spectra.py	47.77%	94 Missing :warning:
...curve_fitting/differentiable_models/PyMC3Models.py	1.40%	70 Missing :warning:
...ightcurve_fitting/differentiable_models/GPModel.py	5.47%	69 Missing :warning:
...ureka/S5_lightcurve_fitting/models/BatmanModels.py	61.01%	23 Missing :warning:
...curve_fitting/differentiable_models/StarryModel.py	0.00%	10 Missing :warning:
...c/eureka/S5_lightcurve_fitting/gradient_fitters.py	9.09%	10 Missing :warning:
src/eureka/S5_lightcurve_fitting/lightcurve.py	57.14%	6 Missing :warning:
src/eureka/S5_lightcurve_fitting/likelihood.py	62.50%	6 Missing :warning:
...rve_fitting/differentiable_models/CentroidModel.py	16.66%	5 Missing :warning:
...urve_fitting/differentiable_models/ExpRampModel.py	16.66%	5 Missing :warning:
... and 14 more

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #659 +/- ## ========================================== - Coverage 54.24% 54.01% -0.23% ========================================== Files 101 101 Lines 12793 12942 +149 ========================================== + Hits 6939 6991 +52 - Misses 5854 5951 +97 ```

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[taylorbell57]

Alright, this PR is now known to work well through to Stage 5, but I haven't yet tested to see what impact this has on Stage 6. My suspicion is that Stage 6 will merge together the spectra of all planets, so I'll likely need to address that