Review behavior of Windows registry functions

Issue

Sentry is receiving events such as:

Couldn't delete 'Nuxeo Drive' value from 'Software\\Microsoft\\Windows\\CurrentVersion\\Run'
FileNotFoundError: [WinError 2] Le fichier spécifié est introuvable

In this case, if the key does not exist, it is OK as we would like to delete it.

Fix

Review all registry functions to adapt the behavior in those cases and add tests.