RFR: JDK-8275308: Add valueOf(Runtime.Version) factory to SourceVersion [v4]

[Joe Darcy]

> I wanted to get input on the design of API of the method before writing the tests.
> 
> The new factory method maps from a Runtime.Version object, a object which formally modes the version of the JDK, to a corresponding SourceVersion object.
> 
> Given the current histories of versioning of the JDK and SourceVersion this amount to mapping "JDK N" to RELEASE_N, for example, JDK 17 to RELEASE_17, etc. As mentioned in the API note, this could potentially change in the future if the release model changes. Runtime.Version has added in JDK 9, but earlier versions can be modeled. Note that no attempt is made to map "1.2" to RELEASE_2 and that since Runtime.Version grammar does not allow a leading 0 term, RELEASE_0 will *not* be returned by the new method.
> 
> Another design point: an out-of-range feature version is treated as an error so a Runtime.Version with a feature of 19 mapped in JDK 18 will fail with an IllegalArgumentException rather than saturating at RELEASE_18. If saturating would be more helpful for the envisioned use cases, I'm open to changing the spec accordingly.
> 
> CSR to follow once the API is nailed down.

Joe Darcy 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 seven additional commits since the last revision:

 - Appease jcheck.
 - Initial test support.
 - Merge branch 'master' into JDK-8275308
 - Add support for reverse conversion.
 - Merge branch 'master' into JDK-8275308
 - Fix typo.
 - JDK-8275308: Add valueOf(Runtime.Version) factory to SourceVersio

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/5973/files
  - new: https://git.openjdk.java.net/jdk/pull/5973/files/2062fd43..091e268b

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=5973&range=03
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=5973&range=02-03

  Stats: 8405 lines in 264 files changed: 6472 ins; 1205 del; 728 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5973.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5973/head:pull/5973

PR: https://git.openjdk.java.net/jdk/pull/5973