I realized while working on lucie that *everyone* uses smallvec 1.x, which functions the same as the many 2.0 alphas. So let's not duplicate dependencies for no good reason.
Let it die, let it die! You shall die
Instead of creating an environment that lives throughout the duration of the process, we now hold the environment options we commit, and create the environment from those options (or grab the current env) whenever we need it. When all holders of the environment are dropped, the environment is dropped as well.
Previously, we held `Environment` as a static variable. Statics are never dropped, but ONNX Runtime's own destructors assumes that the environment is long gone by the time the process exits, which was not the case in `ort`! This led to issues like #441 and the dumb `0003-leak-logger-mutex.patch` from `ort-artifacts`.
