Integrated: 8257028: [type-restrictions] Assorted issues with generation of RestrictedField attributes from annotations

[Srikanth Adayapalam]

- Fix trouble with type annotating reference projection type
    - Change retention of experimental annotation to SOURCE
    - Fix javac crash with separate compilation
    - Improve robusness of tests

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Commit messages:
 - 8257028: [type-restrictions] Assorted issues with generation of RestrictedField attributes from annotations

Changes: https://git.openjdk.java.net/valhalla/pull/278/files
 Webrev: https://webrevs.openjdk.java.net/?repo=valhalla&pr=278&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8257028
  Stats: 171 lines in 6 files changed: 119 ins; 21 del; 31 mod
  Patch: https://git.openjdk.java.net/valhalla/pull/278.diff
  Fetch: git fetch https://git.openjdk.java.net/valhalla pull/278/head:pull/278

PR: https://git.openjdk.java.net/valhalla/pull/278