[modernize] Modernize internal autodiff and numeric_diff logic

Refactor the core automatic and numeric differentiation internal helpers
to utilize C++17 features for improved readability and maintainability:

- Added IntegerSequenceTraits to provide a uniform compile-time interface
  for accessing head and tail of std::integer_sequence.
- Eliminated recursive template meta-programming in autodiff.h, replacing
  it with fold expressions and std::index_sequence.
- Simplified core helper functions like Make1stOrderPerturbation into
  unrolled loops.
- Refactored EvaluateJacobianForParameterBlocks from a recursive struct
  to a recursive function template using if constexpr.
- Updated NumericDiffCostFunction and NumericDiffFirstOrderFunction
  to use the modernized internal helper API.

Change-Id: I934034f7434fc05a8855565b2b534d325f920584

include/ceres/numeric_diff_cost_function.h

@@ -266,14 +266,15 @@ class NumericDiffCostFunction final
              sizeof(double) * ParameterDims::GetDim(block));
     }
 
-    internal::EvaluateJacobianForParameterBlocks<ParameterDims>::
-        template Apply<kMethod, kNumResiduals>(
-            functor_.get(),
-            residuals,
-            options_,
-            this->num_residuals(),
-            parameters_reference_copy.data(),
-            jacobians);
+    internal::EvaluateJacobianForParameterBlocks<kMethod,
+                                                 kNumResiduals,
+                                                 ParameterDims>(
+        functor_.get(),
+        residuals,
+        options_,
+        this->num_residuals(),
+        parameters_reference_copy.data(),
+        jacobians);
 
     return true;
   }