[jdk25u] RFR: 8367692: RISC-V: Align post call nop

[Fei Yang]

Same issue exist in jdk25u repo as well. (Attention @robehn)
Backport is not clean as we don't have fix for https://bugs.openjdk.org/browse/JDK-8358821 in this repo.
So I have to keep `NativeIllegalInstruction::insert` as it is still used in this repo.
Run full tier1-tier3 tests with fastdebug build on linux-riscv64 platform.

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Commit messages:
 - 8367692: RISC-V: Align post call nop

Changes: https://git.openjdk.org/jdk25u/pull/280/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk25u&pr=280&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8367692
  Stats: 134 lines in 7 files changed: 76 ins; 18 del; 40 mod
  Patch: https://git.openjdk.org/jdk25u/pull/280.diff
  Fetch: git fetch https://git.openjdk.org/jdk25u.git pull/280/head:pull/280

PR: https://git.openjdk.org/jdk25u/pull/280