[jdk17u] RFR: 8268294: Reusing HttpClient in a WebSocket.Listener hangs.

[Alex Kasko]

Clean backport of the WebSocket fix.

Additiona testing:

 - [x] checked that jtreg:jdk/java/net/httpclient/websocket/java.net.http/ tests pass with the patch; these updated tests are not runnable without the patch due to MessageEncoder internal API change

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Commit messages:
 - Backport 2d088fa91d18252a801db3b84ff87e261d63ebd4

Changes: https://git.openjdk.java.net/jdk17u/pull/246/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk17u&pr=246&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8268294
  Stats: 1066 lines in 12 files changed: 1054 ins; 0 del; 12 mod
  Patch: https://git.openjdk.java.net/jdk17u/pull/246.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk17u pull/246/head:pull/246

PR: https://git.openjdk.java.net/jdk17u/pull/246