These tests will be a lot less flaky now since they won't depend on
sleeping the current thread, so they won't be susceptible to slow
running CI.
Additionally, we can use `seconds` instead of `milliseconds` which will
remove imprecision errors when determining if the time was over the
threshold.
Thanks to @aboedo for the suggestion.
### Changes
- Moved signature verification files and tests to new `Security` folder
- Moved `CacheFetchPolicy` inside `Caching`
- Split files inside `Misc` into subfolders
Facundo Menzella