RFR: 8320001: javac crashes while adding type annotations to constructor's return type

[Vicente Romero]

Fix for [1] introduced a regression that is making some internal tests fail. Basically fix for [1] is trying to add annotations read from the class file to the corresponding symbol. Constructors are a bit special given that its return type is `void` thus type annotations can't be added to them. This fix is proposing just dropping the type annotation if it applies to the return type of a constructor.

TIA
[1] https://bugs.openjdk.org/browse/JDK-8225377

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

Commit messages:
 - 8320001: javac crashes while adding type annotations to constructor's return type

Changes: https://git.openjdk.org/jdk/pull/16774/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16774&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8320001
  Stats: 151 lines in 2 files changed: 150 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/16774.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16774/head:pull/16774

PR: https://git.openjdk.org/jdk/pull/16774