RFR: 8353344: RISC-V: Detect and enable several extensions for debug builds

[Fei Yang]

Hi, please consider this small change.
Some riscv extesions are in experimental status due to lack of hardware implementations.
They won't be auto enabled at startup even through they could be detected through linux hwprobe syscall.
To ensure they get some proper correctness test-coverage, this turns on some of them for debug builds.
This follows the order of linux hwprobe syscall macro definitions [1]. I can consider adding more if this makes sense.
Manually tested on the command line with fastdebug build using qemu-system (kernel-6.11).

[1] https://github.com/openjdk/jdk/blob/master/src/hotspot/os_cpu/linux_riscv/riscv_hwprobe.cpp#L46-L82

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Commit messages:
 - 8353344: RISC-V: Detect and enable several extensions for debug builds

Changes: https://git.openjdk.org/jdk/pull/24344/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=24344&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8353344
  Stats: 25 lines in 1 file changed: 25 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/24344.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24344/head:pull/24344

PR: https://git.openjdk.org/jdk/pull/24344