RFR 8251989: Hex formatter and parser utility

[Roger Riggs]

Please review updates to the formatting and parsing API based on the 
last round of comments.
There are many changes, so it may be useful to read it as a fresh draft.

  - Rename classes: Encoder -> Formatter; Decoder -> Parser
  - Rename methods: encode -> format; decode -> parse, etc.
  - Rename factory methods to match
  - Added a factory method and re-arrange arguments to make it more 
convenient
    to create uppercase formatters based on the existing uses.
  - The implementation has been updated based on the suggestions and API 
changes

The webrev for applying the API to the security classes will be updated 
when the API settles down.

JavaDoc:
http://cr.openjdk.java.net/~rriggs/hex-formatter/java.base/java/util/Hex.html 


Webrev:
   http://cr.openjdk.java.net/~rriggs/webrev-hex-formatter-8251989/

CSR:
https://bugs.openjdk.java.net/browse/JDK-8251991

p.s.
The previous (encoder/decoder) javadoc has been renamed to:
    http://cr.openjdk.java.net/~rriggs/hex-encoder-javadoc/