RFR: 8296789: <TAB>-completion in jshell fails to expose synthetic bridge methods

[Adam Sotona]

Jshell does not propose completion for members declared in inaccessible parent classes (for example AbstractStringBuilder).

This patch fixes the completion in SourceCodeAnalysisImpl using MethodSymbols and VarSymbols clones with altered enclosing elements. For documentation purpose (print of the enclosing classes) the original enclosing element is restored.

The patch also includes new CompletionSuggestionTest::testPerentMembers
 
Please review.

Thanks,
Adam

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Commit messages:
 - 8296789: <TAB>-completion in jshell fails to expose synthetic bridge methods

Changes: https://git.openjdk.org/jdk/pull/11814/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=11814&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8296789
  Stats: 24 lines in 2 files changed: 19 ins; 0 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/11814.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11814/head:pull/11814

PR: https://git.openjdk.org/jdk/pull/11814