[riscv-port-jdk17u:riscv-port] RFR: 8294187: RISC-V: Unify all relocations for the backend into AbstractAssembler::relocate()

[Xiaolin Zheng]

Tested along with remaining patches, hotspot tier1~4 with fastdebug build.

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Commit messages:
 - 8294187: RISC-V: Unify all relocations for the backend into AbstractAssembler::relocate()

Changes: https://git.openjdk.org/riscv-port-jdk17u/pull/24/files
 Webrev: https://webrevs.openjdk.org/?repo=riscv-port-jdk17u&pr=24&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8294187
  Stats: 33 lines in 7 files changed: 3 ins; 18 del; 12 mod
  Patch: https://git.openjdk.org/riscv-port-jdk17u/pull/24.diff
  Fetch: git fetch https://git.openjdk.org/riscv-port-jdk17u.git pull/24/head:pull/24

PR: https://git.openjdk.org/riscv-port-jdk17u/pull/24