RFR: 8290154: [JVMCI] Implement JVMCI for RISC-V [v2]

[Sacha Coppey]

> This patch adds a JVMCI implementation for RISC-V. It creates the jdk.vm.ci.riscv64 and jdk.vm.ci.hotspot.riscv64 packages, as well as implements a part of jvmciCodeInstaller_riscv64.cpp. To check for correctness, it enables JVMCI code installation tests on RISC-V. It should be tested soon in GraalVM Native Image as well.

Sacha Coppey has refreshed the contents of this pull request, and previous commits have been removed. The incremental views will show differences compared to the previous content of the PR. The pull request contains one new commit since the last revision:

  8290154: [JVMCI] Implement JVMCI for RISC-V

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Changes:
  - all: https://git.openjdk.org/jdk/pull/9587/files
  - new: https://git.openjdk.org/jdk/pull/9587/files/df247c0b..68882a86

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=9587&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=9587&range=00-01

  Stats: 7 lines in 1 file changed: 2 ins; 1 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/9587.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9587/head:pull/9587

PR: https://git.openjdk.org/jdk/pull/9587