Add ability to hash an attribute or value in expression language

Similar to 6255

In expression language it would be very useful to hash arbitrary data or attributes from the incoming flow file.  For example, if the incoming flow file has an attribute called 'serial_num', the user can hash this value in expression language like `${hash('MD5', 'serial_num')}` or similar syntax.

Today users need to add a CryptographicHashAttribute processor to accomplish this.