RFR: 8251989: Hex formatting and parsing utility [v20]

[Roger Riggs]

> java.util.HexFormat utility:
> 
>  - Format and parse hexadecimal strings, with parameters for delimiter, prefix, suffix and upper/lowercase
>  - Static factories and builder methods to create HexFormat copies with modified parameters.
>  - Consistent naming of methods for conversion of byte arrays to formatted strings and back: formatHex and parseHex
>  - Consistent naming of methods for conversion of primitive types: toHexDigits... and fromHexDigits...
>  - Prefix and suffixes now apply to each formatted value, not the string as a whole
>  - Using java.util.Appendable as a target for buffered conversions so output to Writers and PrintStreams
>    like System.out are supported in addition to StringBuilder. (IOExceptions are converted to unchecked exceptions)
>  - Immutable and thread safe, a "value-based" class
> 
> See the [HexFormat javadoc](http://cr.openjdk.java.net/~rriggs/8251989-hex-formatter/java.base/java/util/HexFormat.html) for details.
> 
> Review comments and suggestions welcome.

Roger Riggs has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains 33 additional commits since the last revision:

 - Correct typos in fromHexDigits methods javadoc
 - Merge branch 'master' into 8251989-hex-formatter
 - Merge branch 'master' into 8251989-hex-formatter
 - Clarified parsing of hex as unsigned in fromHexDigits methods.
 - Added @apiNote to fromHexDigits methods to link and compare to similar methods in Integer and Long.
 - Merge branch 'master' into 8251989-hex-formatter
 - Add class level clarification of use of uppercase for primitive conversions
   Switched order of declaration of a couple of method to make the javadoc sequence easier to read
 - Clarify that the fromHexDigit method does not use the prefix, suffix, delimiter, or uppercase parameter.
 - Clarify that the fromHexDigits does not use the uppercase parameter.
 - Increased memory to 4G for the test and add diagnostic info for OOME
 - ... and 23 more: https://git.openjdk.java.net/jdk/compare/912990ca...4866a0a2

-------------

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/482/files
  - new: https://git.openjdk.java.net/jdk/pull/482/files/044d4633..4866a0a2

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=482&range=19
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=482&range=18-19

  Stats: 32400 lines in 831 files changed: 23862 ins; 5860 del; 2678 mod
  Patch: https://git.openjdk.java.net/jdk/pull/482.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/482/head:pull/482

PR: https://git.openjdk.java.net/jdk/pull/482