Lsqfit

Fixes missing file issue in v12.0.2.

Fixes installation issue with Python 3.10.

Bug fix for ``lsqfit.gammaQ`` when ``gsl`` is not installed.

Removes ``lsqfit.BayesIntegrator`` (and ``BayesPDF``) which is replaced by the more capable ``vegas.PDFIntegrator`` in the ``vegas`` module (for multi-dimensional integration). Adds two new methods to ``nonlinear_fit``, for use with ``PDFIntegrator``: ``logpdf(p)`` and ``pdf(p)``.

Fixes for uncommon bugs when ``maxit=0`` or when using the ``noise`` parameter with no prior.

Fixes a bug in ``empbayes_fit(z0, ...)`` that occurred when ``z0`` was an integer or contained integers. Also adds keyword ``chained`` to ``MultiFitter.lsqfit()`` and a new method ``MultiFitter.embayes_fit`` that is the analogue of ``lsqfit.empbayes_fit`` but for a ``MultiFitter``. Thanks to Nollan Miller for pointing out the bug and suggesting the added feature.

Minor update addressing a feature request: new method ``nonlinear_fit.evalchi2(p)``.