Call pluggable EP's shutdown function in Environment::~Environment() (#11120)
I disabled some tests temporarily. I will move them to a separated executable file in another PR.
In the future, I want to combine onnxruntime::Environment and OrtEnv classes. Now we have 3 env classes, it is too confusing:
1. onnxruntime::Env
2. onnxruntime::Environment
3. OrtEnv
Our python binding uses onnxruntime::Environment, while all other language bindings use OrtEnv. So python doesn't unload EPs but the others do. It's better to make them consistent.
Please note even I added the call, currently the unload function still is a no-op on Linux. So, currently on Windows we must unload the EPs while on Linux we must not do it.