Improve Enzyme batch size and gradient

[gdalle]

DI extensions

Enzyme:

• Threshold batch size to input size (to avoid propagating 16 tangents when the input has size 2)
• Use Enzyme.gradient instead of Enzyme.autodiff for out-of-place operations, because it works with StaticArrays out of the box (see also Test Enzyme with StaticArrays #558)

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.39%. Comparing base (3470e14) to head (5944472).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #557   +/-   ##
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  Coverage   98.39%   98.39%           
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  Files         107      107           
  Lines        4739     4739           
=======================================
  Hits         4663     4663           
  Misses         76       76           

Flag	Coverage Δ
DI	98.63% <100.00%> (ø)
DIT	97.90% <ø> (ø)

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