[jdk26u] RFR: 8373808: Refactor java/net/httpclient qpack and hpack tests to use JUnit

[Vanitha B P]

Clean Backport.

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Commit messages:
 - Backport 40755afdf9061d65dfd039a9707445188bc04303

Changes: https://git.openjdk.org/jdk26u/pull/32/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk26u&pr=32&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8373808
  Stats: 497 lines in 31 files changed: 99 ins; 70 del; 328 mod
  Patch: https://git.openjdk.org/jdk26u/pull/32.diff
  Fetch: git fetch https://git.openjdk.org/jdk26u.git pull/32/head:pull/32

PR: https://git.openjdk.org/jdk26u/pull/32