RFR: 8318662: Refactor some jdk/java/net/httpclient/http2 tests to JUnit [v4]

[Mahendra Chhipa]

> Refactoring following httpclient/http2 testng test to JUnit :
> test/jdk/java/net/httpclient/http2/BadHeadersTest.java
> test/jdk/java/net/httpclient/http2/BadPushPromiseTest.java
> test/jdk/java/net/httpclient/http2/BasicTest.java
> test/jdk/java/net/httpclient/http2/ConnectionFlowControlTest.java
> test/jdk/java/net/httpclient/http2/ContinuationFrameTest.java

Mahendra Chhipa has updated the pull request incrementally with one additional commit since the last revision:

  Reverted few formattings.

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Changes:
  - all: https://git.openjdk.org/jdk/pull/27388/files
  - new: https://git.openjdk.org/jdk/pull/27388/files/f4add754..bd122881

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=27388&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=27388&range=02-03

  Stats: 18 lines in 2 files changed: 0 ins; 0 del; 18 mod
  Patch: https://git.openjdk.org/jdk/pull/27388.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27388/head:pull/27388

PR: https://git.openjdk.org/jdk/pull/27388