Support Block (Chunk) Indexing

[tasansal]

Closes #518, #543, #545, #991.

This feature has been requested many times.
This adds the basic functionality of Dask's dask.array.Array.blocks indexing.

I explained the implementation in detail in #991. Please see details there.

This PR implements #991 and adds tests, tutorial, and docs.

This does allow integer and slice (with step of 1) block indexing, or a mix of the two, for Zarr arrays.

QUESTION

• I wasn't exactly sure where to put it in the change log. Currently its in 2.15.0, however, should I move that to Unreleased section??

TODO:

• Add unit tests and/or doctests in docstrings
• Add docstrings and API docs for any new/modified user-facing classes and functions
• New/modified features documented in docs/tutorial.rst
• Changes documented in docs/release.rst
• GitHub Actions have all passed
• Test coverage is 100% (Codecov passes)

[codecov]

Codecov Report

Merging #1428 (257c903) into main (4132f36) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##              main     #1428    +/-   ##
==========================================
  Coverage   100.00%   100.00%            
==========================================
  Files           37        37            
  Lines        14866     15017   +151     
==========================================
+ Hits         14866     15017   +151     

Impacted Files	Coverage Δ
zarr/core.py	100.00% <100.00%> (ø)
zarr/indexing.py	100.00% <100.00%> (ø)
zarr/tests/test_core.py	100.00% <100.00%> (ø)
zarr/tests/test_indexing.py	100.00% <100.00%> (ø)

[joshmoore]

• I wasn't exactly sure where to put it in the change log. Currently its in 2.15.0, however, should I move that to Unreleased section??

Yes please, and update your comments of 2.15 to be 2.16? Huge thanks!

[tasansal]

• I wasn't exactly sure where to put it in the change log. Currently its in 2.15.0, however, should I move that to Unreleased section??

Yes please, and update your comments of 2.15 to be 2.16? Huge thanks!

Done! Seems like all the CI passed too.

[tasansal]

@joshmoore ready to merge?

[joshmoore]

In general, this looks really well done. I'd still ping a few daskanistas (daskonauts?) for some feedback.

cc: @jrbourbeau @jni but of course others welcome!

[rabernat]

This is a great new feature.