Implement a simple atlas manager widget

[alessandrofelder]

Description

What is this PR

• Bug fix
• Addition of a new feature
• Other

Why is this PR needed?
We want to separate out atlas download and version management from visualisation.

What does this PR do?
brainrender-napari now provides two widgets, one for atlas management, one for atlas visualisation.

References

Will close #148
This is also a step on the way to #128 and #129
I think this is the best quickfix to get us to a better state than now (with docs and released version out-of-sync), so we can focus on other things as core-devs for a while (after some changes to the docs).

How has this PR been tested?

Integration test added. Manager widget was already there and tested under the hood, just not there in napari.

Is this a breaking change?

Minor changes in naming.

Does this PR require an update to the documentation?

Yes, to be addressed with brainglobe/brainglobe.github.io#222

Checklist:

• The code has been tested locally
• Tests have been added to cover all new functionality (unit & integration)
• The documentation has been updated to reflect any changes (is separate issue [BUG] brainrender-napari tutorial is out-of-date brainglobe.github.io#222)
• The code has been formatted with pre-commit

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.06%. Comparing base (e5d6a3b) to head (0deb9b0).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #153      +/-   ##
==========================================
+ Coverage   97.99%   98.06%   +0.06%     
==========================================
  Files          10       11       +1     
  Lines         448      464      +16     
==========================================
+ Hits          439      455      +16     
  Misses          9        9              

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[adamltyson]

LGTM, one tiny suggestion.

I think there's lots of scope to make this easier to use, but I agree that this should just be merged and released, then looked into in the future.

The tests are failing because it took too long to download an atlas. It might be worth giving it a bit more time, GIN can be pretty slow (especially as brainglobe-utils tests are hammering it at the moment).