Replace indexed_shape by a version that uses jit

[Michael-T-McCann]

Followup to #517 that is both fewer lines of code and more flexible in that any indexing expression that is valid for jax arrays should automatically work.

[bwohlberg]

Clever use of jax.numpy.empty. What's the computational cost of redoing the jit on each call? Have you checked that it's not considerably slower than the version it replaces?

[Michael-T-McCann]

Timing with

import scico
import numpy as np
%timeit -n 1 -r 1 scico.numpy.util.indexed_shape((1000, 1000, 1000, 1000), (np.newaxis, ..., slice(0, 10), slice(15, 0, -1)))

Proposed version: ~10 ms, existing version, ~10 µs. So we we 1000x slower but these are small numbers.

[bwohlberg]

I hesitate to merge this PR due to the difference in execution time, and also because the new version of indexed_shape will consume potentially large amounts of memory if JIT is disabled for debugging. I propose the compromise in branch brendt/index_shape: keep the original function, and add this one as a potentially useful reference version that is not used by other package components.