Handle closures with Enzyme

[gdalle]

DI extensions

• Handle the new AutoEnzyme(constant_function=false) by providing Duplicated(f, df) instead of Const(f) to autodiff
• Restrict calls to high-level API to constant_function=true because of Does Enzyme's high-level API assume f is constant? EnzymeAD/Enzyme.jl#1670
• At the moment, constant_function=false will fail for functions that don't close over mutable data. It would require Active or MixedDuplicated to make it work, see Duplicating closures EnzymeAD/Enzyme.jl#1669

DIT source

• Implement make_closure(scenario) which creates a closure over x and y buffers (differentiable data) and calls it instead

DIT tests

• Test the closure scenarios with FiniteDiff (they would fail with ForwardDiff for lack of a Dual cache)

DI tests

• Add tests over closure scenarios for AutoEnzyme(constant_function=false)

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.64%. Comparing base (5419f9a) to head (9641c7c).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #375      +/-   ##
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+ Coverage   96.57%   96.64%   +0.06%     
==========================================
  Files          99      100       +1     
  Lines        4876     4918      +42     
==========================================
+ Hits         4709     4753      +44     
+ Misses        167      165       -2     

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[gdalle]

Regardless of which setting ends up being the default in ADTypes, I could use your help on this one @wsmoses