Question : how to random access or skip during decryption

### Problem:

I have a need to handle large files and service a random address range for decryption.
Looking throgh the exampes I dont see an effecient way to do this.
It seems that the underlying encryption data is framed, but the CryptoInputStream doesn't skip in an input stream, and there isnt a support for a Readable Channel that I am aware of

### Solution:
With the existing API - I could use skip in the InputStream, but this will (as I see it) decrypt and throw away the skipped bytes, with extra I/O and CPU load
With an enhanced implementation we could skip on the input stream to the start of a frame and then decrypt that frame (skipping internally to the offset needed by decodng and thowin a few bytes if needed)

### Out of scope:

Inizia con l’API CryptoInputStream esistente e il relativo comportamento di input della cifratura suddivisa in frame, quindi confronta InputStream.skip con il supporto richiesto per Readable Channel. Il lavoro è completato quando un chiamante può gestire un intervallo di indirizzi casuale cercando il frame pertinente ed evitando la decrittografia e l’I/O per i byte scartati.

Scritto dal modello di indicizzazione a partire dal testo della issue.