Add figure plotting brain mask

[tsalo]

Closes #520.

Changes proposed in this pull request

• Add a reportlet showing the brain mask.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 50.00000% with 13 lines in your changes missing coverage. Please review.

Project coverage is 75.61%. Comparing base (e464b62) to head (4da4e65).
Report is 8 commits behind head on main.

Files with missing lines	Patch %	Lines
aslprep/utils/plotting.py	23.52%	13 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #547      +/-   ##
==========================================
- Coverage   76.06%   75.61%   -0.45%     
==========================================
  Files          38       38              
  Lines        4219     4237      +18     
==========================================
- Hits         3209     3204       -5     
- Misses       1010     1033      +23     

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[tsalo]

Something's up with my recent improvements and the jobs are stalling. I need to figure out what's going on there.

[tsalo]

Here's the figure from test_002 (GE data). The aslref image shouldn't have that terrible sphere around it, so I think something needs to be fixed. Also the brain mask looks terrible.

[tsalo]

Many of the test datasets' brain masks look terrible, but I think that needs to go in a separate PR. The only lingering thing here is whether the changes to the CBF maps look good.

[tsalo]

The positive-only mode has a symmetric colorbar for some reason.

[tsalo]

The positive-only mode looks good now, but the colorbar for the positive+negative mode is centered ~40 (halfway between -20 and 100), so I think I just need to accept that it's going to range from -100 to 100 with a symmetric colorbar :(.

[tsalo]

The results look alright now. I'm going to merge.