Fix hemisphere bug in check_orientation

[alessandrofelder]

Description

What is this PR

• Bug fix
• Addition of a new feature
• Other

Why is this PR needed?

check_orientation gave false information when working with hemispheres

What does this PR do?

Ensures check_orientation info is displayed correctly when working with hemispheres, and adds a test for this too (the test(s) could be more exhaustive, but hopefully sufficient in their current state, given brainreg development beyond maintenance not on our roadmap at the moment)

References

Closes #200

How has this PR been tested?

• manual inspection by @IgorTatarnikov and I
• new test added
• I have locally checked that the new test failed before I made the bugfix commit

Is this a breaking change?

No (apart from fixing faulty behaviour).

Does this PR require an update to the documentation?

Maybe we should specify better the point of view of the check_orientation, and understand that better in the first place - to be tackled in brainglobe/brainglobe.github.io#210

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
• The code has been formatted with pre-commit

[IgorTatarnikov]

Looks good 👍