[AutoDiff] Enable differentiation of generic functions.

- Relax differentiability diagnostic for generic functions.
  - Previously, an error was emitted when attempting to differentiate any
    generic function. Now, diagnose only functions with indirect
    differentiation parameters/result.
- Propagate differentiation associated function generic signature throughout
  differentiation pass.
  - Change `PrimalGenCloner` to inherit `TypeSubstCloner`.
  - Make primal value structs inherit primal function's generic parameters
    and signature.
  - Calculate correct substitution map for `PrimalGenCloner::visitApplyInst`.
    Emit diagnostic when apply instruction's associated function (e.g. VJP)
    has generic requirements unmet by the primal generic environment.
  - Remap types in `AdjointEmitter`.
- Remove manually `@differentiable` attribute where clause conformance
  requirement checks.
  - `GenericSignatureBuilder` already performs checks so manual checks are
     unnecessary.

include/swift/AST/DiagnosticsSIL.def

@@ -368,8 +368,9 @@ ERROR(autodiff_unsupported_type,none,
       "differentiating '%0' is not supported yet", (Type))
 ERROR(autodiff_function_not_differentiable,none,
       "function is not differentiable", ())
-NOTE(autodiff_function_generic_functions_unsupported,none,
-     "differentiating generic functions is not supported yet", ())
+NOTE(autodiff_function_indirect_params_or_result_unsupported,none,
+     "differentiating functions with parameters or result of unknown size "
+     "is not supported yet", ())
 NOTE(autodiff_external_nondifferentiable_function,none,
      "cannot differentiate an external function that has not been marked "
      "'@differentiable'", ())
@@ -386,6 +387,9 @@ NOTE(autodiff_protocol_member_subset_indices_not_differentiable,none,
 NOTE(autodiff_function_subset_indices_not_differentiable,none,
      "function is differentiable only with respect to a smaller subset of "
      "arguments", ())
+NOTE(autodiff_function_assoc_func_requirements_unmet,none,
+     "function call is not differentiate because generic requirements are not "
+     "met", ())
 NOTE(autodiff_opaque_function_not_differentiable,none,
      "opaque non-'@autodiff' function is not differentiable", ())
 NOTE(autodiff_property_not_differentiable,none,

lib/SIL/SILFunctionType.cpp

@@ -289,9 +289,6 @@ CanSILFunctionType SILFunctionType::getAutoDiffAssociatedFunctionType(
         /*genericSignature*/ nullptr, ExtInfo(), SILCoroutineKind::None,
         ParameterConvention::Direct_Guaranteed, tangentParams, {},
         tangentResults, None, ctx);
-    SmallVector<SILResultInfo, 8> jvpResults(
-        curryLevels.back()->getResults().begin(),
-        curryLevels.back()->getResults().end());
     break;
   }
   case AutoDiffAssociatedFunctionKind::VJP: {