[riscv-port] RFR: 8279344: riscv: RVB: Add bitwise rotation instructions

[Feilong Jiang]

This PR implements bitwise instructions of RISC-V BitManipulation Extension, including ror/rolw/ror/rori/roriw/rorw.

This PR also add zext/bext C2 instructions that were missed in JDK-8279213

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Commit messages:
 - 8279344: riscv: RVB: Add bitwise rotation instructions

Changes: https://git.openjdk.java.net/riscv-port/pull/39/files
 Webrev: https://webrevs.openjdk.java.net/?repo=riscv-port&pr=39&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8279344
  Stats: 417 lines in 6 files changed: 396 ins; 1 del; 20 mod
  Patch: https://git.openjdk.java.net/riscv-port/pull/39.diff
  Fetch: git fetch https://git.openjdk.java.net/riscv-port pull/39/head:pull/39

PR: https://git.openjdk.java.net/riscv-port/pull/39