Phiml

Fixes NumPy compatibility and other bug fixes, adds convenience features.

Bug fixes, improved CompactSparseTensor support.

**New features**

* Sparse SciPy and ML tensors can now be wrapped like regular tensors.
* Shorthand `shape & dual` to add corresponding dual dims
* Added experimental compact sparse tensor
* Removing dims from a `Shape` can now be done using the `-` operator.
* Generic type conversion via `Shape.as_type()`.

**Improvements**

* `scatter()` is now more flexible with `treat_as_batch` argument.
* Improvements to linear tracing. Improved rank deficiency detection. Linear solves will only use matrix_offset if confirmed by user.
* `minimum` and `maximum` can now be used with `None` values.
* Stacked trees may now include `None` values.
* `reshaped_native()` and `reshaped_numpy()` now support `()` / `None` for singleton dims

Numerous fixes and various new features, see 6

**Highlights**

* JAX buffer management for variable-sized tensors
* JIT improvements and fixes
* Periodic pairwise_differences() and fixes
* Extrapolation by side with '+' and '-'
* Added `substeps` to `iterate()`
* Regularized linear solves for singular matrices
* Add `safe_mul()`