RFR: 8256299: Implement JEP 396: Strongly Encapsulate JDK Internals by Default [v6]

[Mark Reinhold]

> Please review this implementation of JEP 396 (https://openjdk.java.net/jeps/396).
> Alan Bateman is the original author; I’ve credited him in the commit metadata.
> Passes tiers 1-3 on {linux,macos,windows}-x64 and linux-aarch64.

Mark Reinhold has updated the pull request incrementally with one additional commit since the last revision:

  Fix "Add-Exports" case for the setAccessibleNonPublicMemberNonExportedPackage test (v2)

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/1324/files
  - new: https://git.openjdk.java.net/jdk/pull/1324/files/1a7ab4e0..0c9654a0

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=1324&range=05
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=1324&range=04-05

  Stats: 5 lines in 1 file changed: 1 ins; 1 del; 3 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1324.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1324/head:pull/1324

PR: https://git.openjdk.java.net/jdk/pull/1324