[jdk21u-dev] RFR: 8316580: HttpClient with StructuredTaskScope does not close when a task fails

[Alexey Bakhtin]

Please review the backport of JDK-8316580

The backport is almost clean, with an exception for src/java.net.http/share/classes/jdk/internal/net/http/MultiExchange.java
The manual merge is required for MultiExchange::cancel(boolean mayInterruptIfRunning) because of no 8310330 in JDK21

All jtreg tests for java.net.httpclient are passed

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Commit messages:
 - Backport fc98998627443d6e73ac70661f47f48b30525712

Changes: https://git.openjdk.org/jdk21u-dev/pull/1416/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=1416&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8316580
  Stats: 463 lines in 4 files changed: 439 ins; 10 del; 14 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/1416.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/1416/head:pull/1416

PR: https://git.openjdk.org/jdk21u-dev/pull/1416