Add support for caching deks for a very short period of time to support time sensitive operations

[coltfred]

There are cases where an operation can't handle the latency of calling to the TSP during the operation. Or for cases where the dek should be re-used 10s or 100s of times in a row. In these cases we should support a time limited decryptor and encryptor. This would allow these operations to take place in a time sensitive way.

On close the decryptor and encryptor should report their usage back to the TSP. The DEK should be zerod out and there should be a time limit on the amount of time the DEK can be cached for.

[coltfred]

#157 is the WIP PR for this.