RFR: 8304913: Use OperatingSystem, Architecture, and Version in jlink [v3]

[Roger Riggs]

> Refactor the Platform class of jlink to use jdk.internal.util OperatingSystem and Architecture instead of os.name and os.arch. 
> They are direct replacements for the Platform enums except for UNKNOWN; its use is refactored to report errors via exceptions.
> 
> Neither os.name nor os.arch should be assumed to be changeable; 
> one test case is removed because it assumes os.name can be changed on the command line.

Roger Riggs has updated the pull request incrementally with one additional commit since the last revision:

  Source code cleanup suggested by reviewers

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/13585/files
  - new: https://git.openjdk.org/jdk/pull/13585/files/5bf9a506..cfc404c1

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13585&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13585&range=01-02

  Stats: 5 lines in 2 files changed: 0 ins; 0 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/13585.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13585/head:pull/13585

PR: https://git.openjdk.org/jdk/pull/13585