RFR: 8374434: Several JShell tests report JUnit discovery warnings

[Jan Lahoda]

JShell tests where converted to use JUnit instead of TestNG by this commit:
https://github.com/openjdk/jdk/commit/b0ca9bf61e0390a3b022a0915eacabb0cfd92e93

As part of the conversion, the `@Test` annotation had to be copied from classes to test methods, as JUnit requires every test method to be annotated. Sadly the tool doing the conversion moved the annotation to some non-test methods as well. This PR fixes that. The tool has been fixed as well.

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Commit messages:
 - 8374434: Several JShell tests report JUnit discovery warnings

Changes: https://git.openjdk.org/jdk/pull/29034/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=29034&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8374434
  Stats: 4 lines in 3 files changed: 0 ins; 4 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/29034.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29034/head:pull/29034

PR: https://git.openjdk.org/jdk/pull/29034