[Build] Support build with source code of Paddle2ONNX (#1559)

* Add notes for tensors

* Optimize some apis

* move some warnings

* Support build with Paddle2ONNX

* Add protobuf support

* Fix compile on mac

* add clearn package script

* Add paddle2onnx code

* remove submodule

* Add onnx ocde

* remove softlink

* add onnx code

* fix error

* Add cmake file

* fix patchelf

* update paddle2onnx

* Delete .gitmodules

---------

Co-authored-by: PaddleCI <paddle_ci@example.com>
Co-authored-by: pangyoki <pangyoki@126.com>
Co-authored-by: jiangjiajun <jiangjiajun@baidu.lcom>

third_party/optimizer/onnxoptimizer/passes/extract_constant_to_initializer.h

@@ -0,0 +1,62 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+// ATTENTION: The code in this file is highly EXPERIMENTAL.
+// Adventurous users should note that the APIs will probably change.
+
+#pragma once
+
+// Before:
+//	 A = Constant()
+// After:
+//	 A is in the initializer list
+//
+//	 this pass can handle the case satisfy all following conditions:
+//	   condition 1: A is the output of a Constant node
+#include "onnx/common/assertions.h"
+#include "onnxoptimizer/pass.h"
+
+namespace ONNX_NAMESPACE {
+namespace optimization {
+
+struct ExtractConstantToInitializer final : public PredicateBasedPass {
+  explicit ExtractConstantToInitializer()
+      : PredicateBasedPass(PassType::Nop, PassEfficiency::Complete,
+                           PassOptimizationType::Memory) {}
+
+  std::string getPassName() const override {
+    return "extract_constant_to_initializer";
+  }
+
+  bool patternMatchPredicate(Node* node) override {
+    return node->kind() == kConstant;
+  }
+
+  bool runTransform(Node* node, Graph& graph,
+                    NodeDestroyType& destroy_current) override {
+    Tensor t = node->t(kvalue);
+    Value* new_init;
+    if (node->output()->has_unique_name() &&
+        std::find(graph.outputs().rbegin(), graph.outputs().rend(),
+                  node->output()) == graph.outputs().rend()) {
+      new_init = graph.addInitializerAndInput(t, node->output()->uniqueName());
+      node->output()->setUniqueName(
+          ONNX_NAMESPACE::to_string(graph.getNextUnique()), false);
+    } else {
+      // the unique_name will be set in `replaceAllUsesWith` if
+      // node->output() is in graph output
+      new_init = graph.addInitializerAndInput(t);
+    }
+    const bool replacing_success =
+        tryReplacingAllUsesWith(node->output(), new_init);
+    if (!replacing_success) {
+      return false;
+    }
+    destroy_current = NodeDestroyType::DestroyOne;
+    return true;
+  }
+};
+
+}  // namespace optimization
+}  // namespace ONNX_NAMESPACE