[riscv-port-jdk11u:riscv-port] RFR: 8297715: RISC-V: C2: Use single-bit instructions from the Zbs extension

[Gui Cao]

Hi,
Please help review this backport to riscv-port-jdk11u.
Backport of [JDK-8297715](https://bugs.openjdk.org/browse/JDK-8297715).
The original patch cannot be directly applied because of  we use `experimental(bool, UseZbs, false, "Use Zbs instructions")` in riscv-port-jdk11u instead of OpenJDK higher version`product(bool, UseZbs, false, EXPERIMENTAL, "Use Zbs instructions")`

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

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Commit messages:
 - Backport 8297715: RISC-V: C2: Use single-bit instructions from the Zbs extension

Changes: https://git.openjdk.org/riscv-port-jdk11u/pull/21/files
  Webrev: https://webrevs.openjdk.org/?repo=riscv-port-jdk11u&pr=21&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8297715
  Stats: 26 lines in 4 files changed: 25 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/riscv-port-jdk11u/pull/21.diff
  Fetch: git fetch https://git.openjdk.org/riscv-port-jdk11u.git pull/21/head:pull/21

PR: https://git.openjdk.org/riscv-port-jdk11u/pull/21