Add AD1 loader and filesystem

[JSCU-CNI]

Companion PR of fox-it/dissect.evidence#39.

[codecov]

Codecov Report

❌ Patch coverage is 80.00000% with 16 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.01%. Comparing base (0b743d3) to head (dc5c0ad).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
dissect/target/filesystems/ad1.py	72.88%	16 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1306      +/-   ##
==========================================
+ Coverage   80.96%   81.01%   +0.04%     
==========================================
  Files         381      382       +1     
  Lines       33916    33966      +50     
==========================================
+ Hits        27460    27516      +56     
+ Misses       6456     6450       -6     

Flag	Coverage Δ
unittests	81.01% <80.00%> (+0.04%)	⬆️

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