Remove dependencies on Signer, Certificate, Identity, IdentityScope classes from java.security pkg

The java.security.Signer class is deprecated. Several internal security classes have dependencies on this class (and the subclass sun.security.x509.X500Signer) which can easily be removed. See suggested fix for diffs for those changes. Eliminating this dependency helps reduce the number and size of the security classes in the base module.

The classes that I have removed this dependency from are:

sun.security.x509.CertAndKeyGen
sun.security.pkcs.PKCS10
sun.security.tools.KeyTool
Remove dependencies on the following classes too:
  java.security.Certificate
  java.security.Identity
  java.security.IdentityScope