Camb

* Change PPF switch parameter to give closer to fluid model in extreme modes; changes results, but very similar near LCDM (no unit tests fail)
* Minor doc/compatibility updates

- Added pre-compiled binary wheels for pip installation
- Doc updates including new section on code modification
- Minor fixes/tidies

* CAMBparams can now be saved and restored using repr/eval or pickle in standard cases
* Allow DE fluid w(a) table models with w<-1 as long as do not cross -1
* Removed camb.py
* Misc tidies and compatibility fixes

* Refactor reionization models allowing setting the model via python; added sample ExpReionization alternative to default tanh. Examples added to example notebook.
* Removed dependency on distutils ready for Python 12

* Fixed bug calculating Cl from time sources that affected iterated use in Cobaya
* Increase max transfer redshifts to 256
* Added min_l_logl_sampling parameter to set_accuracy (to set lowest multipole at which sparse log-L sampling is used)
* Added sample transfer function animations to the end of the [example notebook](https://camb.readthedocs.io/en/latest/CAMBdemo.html)

* Updated numerical constants, use latest definitions for Megaparsec, and calculate times in Julian giga-years
* Updated default nnu to 3.044 (from 3.046)
* Updated default BBN model (for helium abundance) to PRIMAT2021
* Support general bias(k,z) for source window functions
* [Fix for HMcode-2020 feedback at low k](https://github.com/cmbant/CAMB/issues/135)
* [Fix get_matter_power_spectrum for cross-spectra](https://github.com/cmbant/CAMB/commit/62886436f515fbdc944d50c76f2c0229fd86bd03)
* Allow read_ini to load directly from a URL
* Minor code tidies

These changes do change numerical results, but only at a level that is irrelevant for near-future observations. But some of the higher-precision unit tests also had to be updated.