RFR: 8344647: JDK-8335989 causes a bad requires flag: ACC_TRANSITIVE error for java.se

[Jan Lahoda]

There is a new preview language feature, `requires transitive java.base;`. And the `java.se` module is permitted to use the feature, without being marked as preview (i.e. the `java.se` module participates in preview). This is currently implemented by the common "participates in preview" way, by checking that `java.base` is exporting `jdk.internal.javac` package to `java.se`.

This common way works OK for internal preview feature and API usage, but turns out it may not be appropriate for this feature: the qualified export of the `jdk.internal.javac` package is not a specified API, it is an implementation detail; and the JLS itself specifies that the `java.se` module is participating in preview.

So this PR proposes to change the way javac handles the `java.se` module: it permits the use of the preview feature based on the module name, instead relying on the internal qualified export.

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Commit messages:
 - Fixing test.
 - 8344647: JDK-8335989 causes a bad requires flag: ACC_TRANSITIVE error for java.se

Changes: https://git.openjdk.org/jdk/pull/22322/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=22322&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8344647
  Stats: 61 lines in 8 files changed: 51 ins; 4 del; 6 mod
  Patch: https://git.openjdk.org/jdk/pull/22322.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22322/head:pull/22322

PR: https://git.openjdk.org/jdk/pull/22322