Revert "fix: simplify the import check of bevdet_vendor package"

This reverts commit eeb670a.

Author: cyn-liu

perception/autoware_tensorrt_bevdet/CMakeLists.txt

@@ -3,9 +3,14 @@ project(autoware_tensorrt_bevdet)
 
 add_compile_options(-std=c++17)
 
+find_package(bevdet_vendor)
+if(NOT ${bevdet_vendor_FOUND})
+  message(WARNING "The bevdet_vendor package is not found. Please check its dependencies.")
+  return()
+endif()
+
 find_package(autoware_cmake REQUIRED)
 autoware_package()
-find_package(bevdet_vendor REQUIRED)
 find_package(rclcpp REQUIRED)
 find_package(rclcpp_components REQUIRED)
 find_package(Eigen3 REQUIRED)