[jdk21u-dev] RFR: 8335181: Incorrect handling of HTTP/2 GOAWAY frames in HttpClient

[Ryan Flegel]

I am backporting this fix because I am being affected by [JDK-8335181](https://bugs.openjdk.org/browse/JDK-8335181). I had to downgrade to HTTP/1.1 in order to use `HttpClient`.

I needed to resolve two minor conflicts in `MultiExchange.java` due to [JDK-8191494](https://bugs.openjdk.org/browse/JDK-8191494) being applied slightly differently in different projects. In both cases, I kept the change closer to upstream.

The conflicts were:
* Explicit vs implicit null field initialization
* Different debug log message

I was unable to run local tests due to this error:

* For target jdk__optimize_image_exec:
Error: Unable to initialize main class build.tools.jigsaw.AddPackagesAttribute
Caused by: java.lang.ClassFormatError: StackMapTable format error: access beyond the end of attribute


However, all tests in the GitHub actions have passed.

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Commit messages:
 - Backport 720b44648bcff997278af92746f942b2425298a5

Changes: https://git.openjdk.org/jdk21u-dev/pull/1020/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=1020&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8335181
  Stats: 631 lines in 12 files changed: 573 ins; 2 del; 56 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/1020.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/1020/head:pull/1020

PR: https://git.openjdk.org/jdk21u-dev/pull/1020