swift

28315487 - [AutoDiff upstream] Serialize derivative function configurations. (#30672)

[AutoDiff upstream] Serialize derivative function configurations. (#30672) Serialize derivative function configurations per module. `@differentiable` and `@derivative` attributes register derivatives for `AbstractFunctionDecl`s for a particular "derivative function configuration": parameter indices and dervative generic signature. To find `@derivative` functions registered in other Swift modules, derivative function configurations must be serialized per module. When configurations for a `AbstractFunctionDecl` are requested, all configurations from imported modules are deserialized. This module serialization technique has precedent: it is used for protocol conformances (e.g. extension declarations for a nominal type) and Obj-C members for a class type. Add `AbstractFunctionDecl::getDerivativeFunctionConfigurations` entry point for accessing derivative function configurations. In the differentiation transform: use `AbstractFunctionDecl::getDerivativeFunctionConfigurations` to implement `findMinimalDerivativeConfiguration` for canonical derivative function configuration lookup, replacing `getMinimalASTDifferentiableAttr`. Resolves TF-1100.