Add missing includes

[wentasah]

Without these, I get the following build errors in latest rolling:

/build/imu_tools-release-release-rolling-rviz_imu_plugin-2.2.4-2/src/imu_display.cpp: In member function 'virtual void rviz_imu_plugin::ImuDisplay::onEnable()':
/build/imu_tools-release-release-rolling-rviz_imu_plugin-2.2.4-2/src/imu_display.cpp:67:16: error: invalid use of incomplete type 'class Ogre::SceneNode'
   67 |     scene_node_->setVisible(true);
      |                ^~
In file included from /build/imu_tools-release-release-rolling-rviz_imu_plugin-2.2.4-2/src/imu_display.h:37,
                 from /build/imu_tools-release-release-rolling-rviz_imu_plugin-2.2.4-2/src/imu_display.cpp:31:
/nix/store/h70jr156g5i17ppcyhfhpvrrxf7zs0li-ros-rolling-rviz-common-16.0.3-r1/include/rviz_common/rviz_common/display.hpp:52:7: note: forward declaration of 'class Ogre::SceneNode'
   52 | class SceneNode;
      |       ^~~~~~~~~
/build/imu_tools-release-release-rolling-rviz_imu_plugin-2.2.4-2/src/imu_display.cpp: In member function 'virtual void rviz_imu_plugin::ImuDisplay::onDisable()':
/build/imu_tools-release-release-rolling-rviz_imu_plugin-2.2.4-2/src/imu_display.cpp:78:16: error: invalid use of incomplete type 'class Ogre::SceneNode'
   78 |     scene_node_->setVisible(false);
      |                ^~
/nix/store/h70jr156g5i17ppcyhfhpvrrxf7zs0li-ros-rolling-rviz-common-16.0.3-r1/include/rviz_common/rviz_common/display.hpp:52:7: note: forward declaration of 'class Ogre::SceneNode'
   52 | class SceneNode;
      |       ^~~~~~~~~
/build/imu_tools-release-release-rolling-rviz_imu_plugin-2.2.4-2/src/imu_display.cpp: In member function 'virtual void rviz_imu_plugin::ImuDisplay::onInitialize()':
/build/imu_tools-release-release-rolling-rviz_imu_plugin-2.2.4-2/src/imu_display.cpp:86:33: error: invalid use of incomplete type 'class Ogre::SceneManager'
   86 |     scene_node_ = scene_manager_->getRootSceneNode()->createChildSceneNode();
      |                                 ^~
/nix/store/h70jr156g5i17ppcyhfhpvrrxf7zs0li-ros-rolling-rviz-common-16.0.3-r1/include/rviz_common/rviz_common/display.hpp:51:7: note: forward declaration of 'class Ogre::SceneManager'
   51 | class SceneManager;
      |       ^~~~~~~~~~~~
/build/imu_tools-release-release-rolling-rviz_imu_plugin-2.2.4-2/src/imu_display.cpp:98:16: error: invalid use of incomplete type 'class Ogre::SceneNode'
   98 |     scene_node_->setVisible(isEnabled());
      |                ^~
/nix/store/h70jr156g5i17ppcyhfhpvrrxf7zs0li-ros-rolling-rviz-common-16.0.3-r1/include/rviz_common/rviz_common/display.hpp:52:7: note: forward declaration of 'class Ogre::SceneNode'
   52 | class SceneNode;
      |       ^~~~~~~~~
/build/imu_tools-release-release-rolling-rviz_imu_plugin-2.2.4-2/src/mag_display.cpp: In member function 'virtual void rviz_imu_plugin::MagDisplay::onEnable()':
/build/imu_tools-release-release-rolling-rviz_imu_plugin-2.2.4-2/src/mag_display.cpp:50:16: error: invalid use of incomplete type 'class Ogre::SceneNode'
   50 |     scene_node_->setVisible(true);
      |                ^~
In file included from /build/imu_tools-release-release-rolling-rviz_imu_plugin-2.2.4-2/src/mag_display.h:37,
                 from /build/imu_tools-release-release-rolling-rviz_imu_plugin-2.2.4-2/src/mag_display.cpp:31:
/nix/store/h70jr156g5i17ppcyhfhpvrrxf7zs0li-ros-rolling-rviz-common-16.0.3-r1/include/rviz_common/rviz_common/display.hpp:52:7: note: forward declaration of 'class Ogre::SceneNode'
   52 | class SceneNode;
      |       ^~~~~~~~~
/build/imu_tools-release-release-rolling-rviz_imu_plugin-2.2.4-2/src/mag_display.cpp: In member function 'virtual void rviz_imu_plugin::MagDisplay::onDisable()':
/build/imu_tools-release-release-rolling-rviz_imu_plugin-2.2.4-2/src/mag_display.cpp:59:16: error: invalid use of incomplete type 'class Ogre::SceneNode'
   59 |     scene_node_->setVisible(false);
      |                ^~
/nix/store/h70jr156g5i17ppcyhfhpvrrxf7zs0li-ros-rolling-rviz-common-16.0.3-r1/include/rviz_common/rviz_common/display.hpp:52:7: note: forward declaration of 'class Ogre::SceneNode'
   52 | class SceneNode;
      |       ^~~~~~~~~
/build/imu_tools-release-release-rolling-rviz_imu_plugin-2.2.4-2/src/mag_display.cpp: In member function 'virtual void rviz_imu_plugin::MagDisplay::onInitialize()':
/build/imu_tools-release-release-rolling-rviz_imu_plugin-2.2.4-2/src/mag_display.cpp:67:33: error: invalid use of incomplete type 'class Ogre::SceneManager'
   67 |     scene_node_ = scene_manager_->getRootSceneNode()->createChildSceneNode();
      |                                 ^~
/nix/store/h70jr156g5i17ppcyhfhpvrrxf7zs0li-ros-rolling-rviz-common-16.0.3-r1/include/rviz_common/rviz_common/display.hpp:51:7: note: forward declaration of 'class Ogre::SceneManager'
   51 | class SceneManager;
      |       ^~~~~~~~~~~~
/build/imu_tools-release-release-rolling-rviz_imu_plugin-2.2.4-2/src/mag_display.cpp:72:16: error: invalid use of incomplete type 'class Ogre::SceneNode'
   72 |     scene_node_->setVisible(isEnabled());
      |                ^~
/nix/store/h70jr156g5i17ppcyhfhpvrrxf7zs0li-ros-rolling-rviz-common-16.0.3-r1/include/rviz_common/rviz_common/display.hpp:52:7: note: forward declaration of 'class Ogre::SceneNode'
   52 | class SceneNode;
      |       ^~~~~~~~~