OpenJPEG Conan wrapper should set CMake name to openjp2

Currently our Conan wrapper around the system installed OpenJPEG library declares:

```
self.cpp_info.set_property("cmake_target_name", "openjpeg::openjpeg")
```

But the full recipe names it `openjp2`:

https://github.com/conan-io/conan-center-index/blob/6e3a464d7858464f57326bb8322473aaba1dd4f9/recipes/openjpeg/all/conanfile.py#L144

and this is what the newly reworked CMake support for OpenJPEG calls it in OIIO 3.1.7.0

We should update our wrapper to match, and this should remove the need for some of our OIIO CMake patches.

Find the OpenJPEG Conan wrapper and inspect the cmake_target_name property, then compare it with the linked Conan Center recipe and OIIO 3.1.7.0's CMake naming. Done means the wrapper uses openjp2 and the change removes the need for the related OIIO CMake patches.

Written by the indexing model from the issue text.