[BREAKING] Force use of Tangents in pushforward, pullback and hvp

[gdalle]

Warning

Breaking change:

• The operators pushforward, pullback and hvp no longer accept plain objects as dx or dy: this argument must now be wrapped into Tangents.

Tip

Since Tangents becomes part of the public API, this also allows users to leverage batch mode directly. At the moment it is only useful with ForwardDiff, but we're working on adding Enzyme support.

DI source

• Force pushforward, pullback and hvp to use Tangents and remove the fallbacks.
• Change the Tangents constructor so that it accepts Vararg, also modify its second type parameter
• Add tuple-like functionalities to Tangents like indexing and map

DI extensions

• Adapt operators for each backend to the new Tangents constructor

DI docs

• Make Tangents part of the public API, enabling users to access batch mode

DIT source

• Modify Scenario constructors so that they only accept Tangents for pushforward, pullback and hvp
• Adapt all scenarios and scenario modifiers accordingly

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.52%. Comparing base (b2dcdef) to head (3b8537b).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #455      +/-   ##
==========================================
- Coverage   98.53%   98.52%   -0.01%     
==========================================
  Files         107      106       -1     
  Lines        4287     4265      -22     
==========================================
- Hits         4224     4202      -22     
  Misses         63       63              

Flag	Coverage Δ
DI	98.67% <100.00%> (-0.02%)	⬇️
DIT	98.21% <100.00%> (ø)

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