Fix FiniteDiff derivative

[gdalle]

DI extensions

• FiniteDiff: use cache for derivative of f!
• ChainRules, Tracker and Zygote: fix preparation dispatch

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 93.63%. Comparing base (7c60378) to head (de041a4).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #436   +/-   ##
=======================================
  Coverage   93.63%   93.63%           
=======================================
  Files         102      102           
  Lines        4885     4886    +1     
=======================================
+ Hits         4574     4575    +1     
  Misses        311      311           

Flag	Coverage Δ
DI	99.27% <100.00%> (+<0.01%)	⬆️
DIT	86.33% <ø> (ø)

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