RFR: 8353950: Clipboard interaction on Windows is unstable [v5]

[Matthias Bläsing]

> - Introduce a lock into WClipboard that protects the code between
>   openClipboard/closeClipboard invocations.
>   The native side does not allow to open the clipboard multiple
>   times or share the opened clipboard between multiple threads.
> 
> - Remove of need to call openClipboard/closeClipboard from
>   getClipboardFormats by using the win32 call
>   GetUpdatedClipboardFormats
> 
> - Prevent a race-condition by not registering the connection
>   between java and native side of clipboard multiple time, but
>   just at construction time.

Matthias Bläsing has updated the pull request incrementally with one additional commit since the last revision:

  Address review comments:
  
  - reduce log level in WClipboard#handleContentsChanged to DEBUG, so that
    in normal operation it will not be visible
  - restore comment on WClipboard#closeClipboard
  - adjust comment on WClipboard#openClipboard
  - Ensure ConcurrentClipboardAccessTest shutsdown on its own when not
    run in an environment with an external timeout handling.
  - Added finishing message to ConcurrentClipboardAccessTest, so that
    correct termination can be determined visually if run manually

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/24614/files
  - new: https://git.openjdk.org/jdk/pull/24614/files/bfa99a71..50ccf766

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=24614&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=24614&range=03-04

  Stats: 18 lines in 2 files changed: 13 ins; 0 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/24614.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24614/head:pull/24614

PR: https://git.openjdk.org/jdk/pull/24614