[jdk21u-dev] RFR: 8339238: Update to use jtreg 7.5.1 [v2]

[Adam Farley]

> Hi all,
> 
> This pull request contains a backport of commit [9042aa82](https://github.com/openjdk/jdk25u-dev/commit/9042aa82a890b0f0348ac8127dbd3268f2620346) from the [openjdk/jdk25u-dev](https://github.com/openjdk/jdk25u-dev) repository.
> 
> The commit being backported was authored by Christian Stein on 19 Feb 2025 and was reviewed by Erik Joelsson, Jaikiran Pai, Roger Riggs and Iris Clark.
> 
> Thanks!

Adam Farley has updated the pull request incrementally with one additional commit since the last revision:

  Compile NativeTestHelper with enable-preview
  
  Because otherwise it will not compile while using jtreg 7.5.1
  as TestNested's enable-preview is not inherited.
  
  Signed-off-by: Adam Farley <adfarley at ibm.com>

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

Changes:
  - all: https://git.openjdk.org/jdk21u-dev/pull/2605/files
  - new: https://git.openjdk.org/jdk21u-dev/pull/2605/files/9164f8ef..36df503e

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=2605&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=2605&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/2605.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/2605/head:pull/2605

PR: https://git.openjdk.org/jdk21u-dev/pull/2605