Implement general kinetic model for multi-PLD data

[tsalo]

Closes #272 and closes #298.

Changes proposed in this pull request

• Replace the weighted average approach from Dai 2012 with the general kinetic model from Buxton 1998, as recommended and expanded in Woods 2023. This works for both multi-PLD PCASL and multi-PLD PASL.
• Add aBAT and aBV outputs for multi-PLD PCASL and PASL.

Documentation that should be reviewed

[tsalo]

I still need to figure out how to get M0b.

[codecov-commenter]

Codecov Report

Attention: 15 lines in your changes are missing coverage. Please review.

Comparison is base (247515a) 79.62% compared to head (5c2c0ed) 79.67%.

Files	Patch %	Lines
aslprep/utils/cbf.py	89.71%	7 Missing and 4 partials ⚠️
aslprep/workflows/asl/cbf.py	42.85%	3 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #381      +/-   ##
==========================================
+ Coverage   79.62%   79.67%   +0.04%     
==========================================
  Files          37       37              
  Lines        3946     4004      +58     
  Branches      551      561      +10     
==========================================
+ Hits         3142     3190      +48     
- Misses        625      633       +8     
- Partials      179      181       +2     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[tsalo]

Closing in favor of #545.