Remove SafeX509Handle finalizations coming out of the test project

Remove SafeX509Handle finalizations coming out of the test project

There are a few classes of problems here
* X509Chain's X509ChainElements have (newly created) X509Certificate2s on them, no one called Dispose.
* Not Disposing the returned results from calls to Find.
* Touching X509Store.Certificates in passing.
    * MachineRootStore_NonEmpty asked for the Count of the root store, sending that number of handles to be Finalized

Commit migrated from https://github.com/dotnet/corefx/commit/67d802cebe2ca7ce6c5668907f382823758ad8f5