RFR: 8247373: ArraysSupport.newLength doc, test, and exception message [v2]

[Stuart Marks]

> This rewrites the doc of ArraysSupport.newLength, adds detail to the exception message, and adds a test. In addition to some renaming and a bit of refactoring of the actual code, I also made two changes of substance to the code:
> 
> 1. I fixed a problem with overflow checking. In the original code, if oldLength and prefGrowth were both very large (say, Integer.MAX_VALUE), this method could return a negative value. It turns out that writing tests helps find bugs!
> 
> 2. Under the old policy, if oldLength and minGrowth required a length above SOFT_MAX_ARRAY_LENGTH but not above Integer.MAX_VALUE, this method would return Integer.MAX_VALUE. That doesn't make any sense, because attempting to allocate an array of that length will almost certainly cause the Hotspot to throw OOME because its implementation limit was exceeded. Instead, if the required length is in this range, this method returns that required length.
> 
> Separately, I'll work on retrofitting various call sites around the JDK to use this method.

Stuart Marks has updated the pull request incrementally with one additional commit since the last revision:

  fix typo, clarify asserts disabled, test prefGrowth==0

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/1617/files
  - new: https://git.openjdk.java.net/jdk/pull/1617/files/03b7922f..bacb5f91

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=1617&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=1617&range=00-01

  Stats: 3 lines in 2 files changed: 2 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1617.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1617/head:pull/1617

PR: https://git.openjdk.java.net/jdk/pull/1617