revert cached kernel context removing (#39055)

paddle/fluid/imperative/layer.cc

@@ -409,6 +409,8 @@ void VarBase::_CopyGradientFrom(const VarBase& src) {
   }
 }
 
+pten::KernelContext OpBase::pt_kernel_context_;
+
 void OpBase::SetType(const std::string& type) {
   op_ = framework::OpRegistry::CreateOp(type, {}, {}, {}, false);
 }

paddle/fluid/imperative/op_base.h

@@ -210,6 +210,9 @@ class OpBase {
   std::unique_ptr<framework::OperatorBase> op_;
   platform::Place place_;
   size_t id_{-1UL};
+  // In order to reduce the compatibility phase
+  // performance overhead, temporarily cache KernelContext
+  static pten::KernelContext pt_kernel_context_;
   std::vector<std::shared_ptr<std::function<void()>>> void_function_post_hooks_;
 };