[riscv-port-jdk11u:riscv-port] RFR: 8309258: RISC-V: Add riscv_hwprobe syscall

[Gui Cao]

Hi, 
Please help review this backport to riscv-port-jdk11u.
Backport of [8309258](https://bugs.openjdk.org/browse/JDK-8309258), [8315206](https://bugs.openjdk.org/browse/JDK-8315206), [8316859](https://bugs.openjdk.org/browse/JDK-8316859), [8324280](https://bugs.openjdk.org/browse/JDK-8324280), [8315652](https://bugs.openjdk.org/browse/JDK-8315652)

Since [8315195](https://bugs.openjdk.org/browse/JDK-8315195) hasn't been backported yet, the RVV,Zba,Zbb extension hasn't been turned on automatically yet.

This backport adds the syscall, uses the syscall in combination with the aux and cpuinfo to enable features by default.

### Testing on SOPHON SG2042

$ ./java -XX:+UnlockExperimentalVMOptions -XX:+PrintFlagsFinal -version | grep Use
     bool UseRVC                                   = true                            {ARCH experimental} {default}
     bool UseRVV                                   = false                           {ARCH experimental} {default}
     bool UseZba                                   = false                           {ARCH experimental} {default}
     bool UseZbb                                   = false                           {ARCH experimental} {default}

test/lib/sun/hotspot/cpuinfo/CPUInfo.java  log like this:

----------System.out:(13/2767)----------
WB.getCPUFeatures(): "qemu rv64 i m a f d c"
CPUInfo.getFeatures(): [qemu, rv64, i, m, a, f, d, c]


### Testing on qemu-system

$ ./java -XX:+UnlockExperimentalVMOptions -XX:+PrintFlagsFinal -version | grep Use
     bool UseRVC                                   = true                            {ARCH experimental} {default}
     bool UseRVV                                   = false                           {ARCH experimental} {default}
     bool UseZba                                   = false                           {ARCH experimental} {default}
     bool UseZbb                                   = false                           {ARCH experimental} {default}

test/lib/sun/hotspot/cpuinfo/CPUInfo.java  log like this:

----------System.out:(13/2290)----------
WB.getCPUFeatures(): "rv64 i m a f d c"
CPUInfo.getFeatures(): [rv64, i, m, a, f, d, c]


### Testing 
- [x] Run tier1 tests on SOPHON SG2042 (release)

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

Commit messages:
 - Backport 8315652: RISC-V: Features string uses wrong separator for jtreg
 - Backport 8309258: RISC-V: Add riscv_hwprobe syscall

Changes: https://git.openjdk.org/riscv-port-jdk11u/pull/20/files
  Webrev: https://webrevs.openjdk.org/?repo=riscv-port-jdk11u&pr=20&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8309258
  Stats: 583 lines in 5 files changed: 475 ins; 47 del; 61 mod
  Patch: https://git.openjdk.org/riscv-port-jdk11u/pull/20.diff
  Fetch: git fetch https://git.openjdk.org/riscv-port-jdk11u.git pull/20/head:pull/20

PR: https://git.openjdk.org/riscv-port-jdk11u/pull/20