[jdk11u-dev] RFR: 8320001: javac crashes while adding type annotations to the return type of a constructor

[Liam Miller-Cushon]

This is a backport of [JDK-8320001: javac crashes while adding type annotations to the return type of a constructor](https://bugs.openjdk.org/browse/JDK-8320001), which fixes a regression introduced by [JDK-8225377: type annotations are not visible to javac plugins across compilation boundaries](https://bugs.openjdk.org/browse/JDK-8225377).

I resolved a trivial merge conflict due to a change on an adjacent line. The test was updated to replace a use of text blocks for Java 11 compatibility.

Testing: included test fails without the fix, and passes with it applied

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Depends on: https://git.openjdk.org/jdk11u-dev/pull/2272

Commit messages:
 - Backport 5e24aaf4f7f11862ec8ac9d5c3e65d614104fb2c

Changes: https://git.openjdk.org/jdk11u-dev/pull/2312/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=2312&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8320001
  Stats: 139 lines in 2 files changed: 138 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/2312.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev.git pull/2312/head:pull/2312

PR: https://git.openjdk.org/jdk11u-dev/pull/2312