Write out GIFTI and CIFTI CBF maps

[tsalo]

Closes #356.

Changes proposed in this pull request

• Stop writing out preprocessed ASL data in GIFTI format.
• Start writing out CBF and ATT data in GIFTI format.
• Fix connections necessary to create CIFTI-format CBF maps.

[codecov-commenter]

Codecov Report

Attention: 2 lines in your changes are missing coverage. Please review.

Comparison is base (8c80d31) 75.99% compared to head (ae9df9c) 78.81%.

Files	Patch %	Lines
aslprep/workflows/asl/resampling.py	93.33%	1 Missing and 1 partial :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #361 +/- ## ========================================== + Coverage 75.99% 78.81% +2.81% ========================================== Files 39 39 Lines 4120 4149 +29 Branches 595 600 +5 ========================================== + Hits 3131 3270 +139 + Misses 791 685 -106 + Partials 198 194 -4 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.