Fix the pipeline which was broken in 4f84c82c .

Move some properties of CoordinateChart to actual properties as to
provide doc-strings for them.

Guess a good `depth` based on `min_shape` if none is specified.

Set the new defaults such that the resulting chart is more precise.

Most notably, extend test_refinement_covariance to also test various
refinement parametrizations.

Adapt to the new error message in JAX for failing to transpose a
refinement field.

Implement a highly efficient refine method for irregular 1D grids.

Instead of a kernel, also accept a set of pre-computed refinement
matrices.

In particular pass on `coerce_fine_kernel`.

Implement an orthogonal approach to modeling GPs: SKI. To be specific,
implement KISS-GP with Toeplitz kernels.

Extends c0912dbb .