Remove potential leaks when type providers are misauthored #6409

(copied and paraphrased over from @dsyme's PR)

The following mistakes in type provider authoring can result in a memory leak:

1. If TP instances have mistakenly kept themselves alive by F# compiler not disposing them correctly
2. If a TP registers itself in global state, e.g. in a callback in a file watch timer or stores itself in global state in its own .dll
3. if a TP saves one of its generated ProvidedTypeDefinition in a global cache in its own .dll

The compiler should be able to still release these resources.