RFR: 8255757: Javac emits duplicate pool entries on array::clone

[Guoxiong Li]

Hi all,

Currently, javac would emit duplicate pool entries when compiling array::clone.
This patch fixes it by using a cached field `Map<Type, Symbol> qualifiedSymbolCache;` and adds a corresponding test case.

Thank you for taking the time to review.

Best Regards.

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

Commit messages:
 - 8255757: Javac emits duplicate pool entries on array::clone

Changes: https://git.openjdk.java.net/jdk/pull/1912/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=1912&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8255757
  Stats: 121 lines in 2 files changed: 119 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1912.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1912/head:pull/1912

PR: https://git.openjdk.java.net/jdk/pull/1912