javax.crypto: update classes in javax.crypto (part 2)

Pulling upstream changes from OpenJDK version jdk8u60 for
SecretKey, SecretKeyFactory and SecretKeyFactorySpi.

- SecretKey now extends javax.security.auth.Destroyable
- Second parameter of SecretKeyFactory#getKeySpec is now Class<?>
instead of Class
- Second parameter of SecretKeyFactorySpi#engineGetKeySpec is now
Class<?> instead of Class

This commit also contains cosmetic JavaDoc changes like
- Use of @code in place of <code> tags.
- Tidied up casts/generics.

Note not all classes in javax.crypto are updated: CipherInputStream,
CipherOutputStream, CipherSpi have changes that deserve a separate CL.

All API changes in the package are ported.

Change-Id: Iaa0ce3e34f9f73260e7b66db601b5cb1462aa854
Test: make droid docs
Bug: 29631070