[lworld] RFR: JDK-8265376: Prepare for javac change to do the member translation as described in SoV

[Mandy Chung]

This updates `test/jdk/valhalla/valuetypes/QTypeDescriptorTest.java` and 
`test/jdk/valhalla/valuetypes/Reflection.java` tests to prepare for the javac
change to do the member translation as described in SoV (JDK-8244313).

It also fixes a bug in `Class::referenceType` to return this class if it's an
identity class.  This was uncovered by this test change.

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Commit messages:
 - JDK-8265376: Prepare for javac change to do the member translation as described in SoV

Changes: https://git.openjdk.java.net/valhalla/pull/387/files
 Webrev: https://webrevs.openjdk.java.net/?repo=valhalla&pr=387&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8265376
  Stats: 109 lines in 3 files changed: 91 ins; 1 del; 17 mod
  Patch: https://git.openjdk.java.net/valhalla/pull/387.diff
  Fetch: git fetch https://git.openjdk.java.net/valhalla pull/387/head:pull/387

PR: https://git.openjdk.java.net/valhalla/pull/387