[jdk17u-dev] RFR: 8316580: HttpClient with StructuredTaskScope does not close when a task fails

[Goetz Lindenmaier]

I backport this for parity with 17.0.17-oracle.

The change applies clean, but the test does not work out-of-the-box.

It calls some utility methods ReferenceTracker.java that were added by JDK-8305847.
That change is not in the current list of backports, so I added the utility methods 
to this change.

Further, the test depends on the fact that in 21 a row of classes implement
AutoClosable, which they don't do in 21.
I adapted a row of places to work around this. 
A try-with-resources statement was easy to replace, as the missing 
close() implementation uses public methods, so that I could copy the
code to the test.
In TestTaskScope I replaced close()  by shutdownNow().
Finally I removed the "useReferenceTracker=false" test variant, as the
HttpClient implementation is quite far off of the implementation in 21.

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

Commit messages:
 - Adapt test to missing AutoClosable etc.
 - Parts of 8305847
 - Backport d8291f593762ab270bf05643b87c57578d716242

Changes: https://git.openjdk.org/jdk17u-dev/pull/3706/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=3706&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8316580
  Stats: 497 lines in 4 files changed: 473 ins; 10 del; 14 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/3706.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/3706/head:pull/3706

PR: https://git.openjdk.org/jdk17u-dev/pull/3706