Revert "Delete TorchScript based Android demo app and point to ExecuTorch (#153633)"

This reverts commit b22f01fcb9d69bb7d77e08d69004c7265ef7fa4a.

Reverted https://github.com/pytorch/pytorch/pull/153633 on behalf of https://github.com/malfet due to But libtorch build regressions are real, fbjni is still used for C++ builds ([comment](https://github.com/pytorch/pytorch/pull/153633#issuecomment-2884951805))

android/pytorch_android/generate_test_asset.cpp

@@ -0,0 +1,20 @@
+#include <torch/csrc/jit/api/module.h>
+#include <torch/jit.h>
+#include <torch/script.h>
+
+#include <fstream>
+#include <iostream>
+#include <string>
+
+int main(int argc, char* argv[]) {
+  std::string input_file_path{argv[1]};
+  std::string output_file_path{argv[2]};
+
+  std::ifstream ifs(input_file_path);
+  std::stringstream buffer;
+  buffer << ifs.rdbuf();
+  torch::jit::Module m("TestModule");
+
+  m.define(buffer.str());
+  m.save(output_file_path);
+}