[riscv-port-jdk17u:riscv-port] RFR: 8305008: RISC-V: Factor out immediate checking functions from assembler_riscv.inline.hpp

[Dingli Zhang]

Hi, please review this backport to riscv-port-jdk17u.
Backport of [JDK-8305008](https://bugs.openjdk.org/browse/JDK-8305008).
The original patch cannot be directly applied because jdk17u has no [JDK-8295948](https://bugs.openjdk.org/browse/JDK-8295948) and [JDK-8294100](https://bugs.openjdk.org/browse/JDK-8294100).

Testing:
- Tier1-3 passed without new failure on unmacthed (release).

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Commit messages:
 - 8305008: RISC-V: Factor out immediate checking functions from assembler_riscv.inline.hpp

Changes: https://git.openjdk.org/riscv-port-jdk17u/pull/63/files
 Webrev: https://webrevs.openjdk.org/?repo=riscv-port-jdk17u&pr=63&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8305008
  Stats: 149 lines in 11 files changed: 20 ins; 13 del; 116 mod
  Patch: https://git.openjdk.org/riscv-port-jdk17u/pull/63.diff
  Fetch: git fetch https://git.openjdk.org/riscv-port-jdk17u.git pull/63/head:pull/63

PR: https://git.openjdk.org/riscv-port-jdk17u/pull/63