[riscv-port-jdk17u:riscv-port] RFR: 8294366: RISC-V: Partially mark out incompressible regions

[Xiaolin Zheng]

One little difference: there is no `C2_MacroAssembler::emit_entry_barrier_stub` on JDK17.

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

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Commit messages:
 - 8294366: RISC-V: Partially mark out incompressible regions

Changes: https://git.openjdk.org/riscv-port-jdk17u/pull/28/files
 Webrev: https://webrevs.openjdk.org/?repo=riscv-port-jdk17u&pr=28&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8294366
  Stats: 109 lines in 7 files changed: 48 ins; 36 del; 25 mod
  Patch: https://git.openjdk.org/riscv-port-jdk17u/pull/28.diff
  Fetch: git fetch https://git.openjdk.org/riscv-port-jdk17u.git pull/28/head:pull/28

PR: https://git.openjdk.org/riscv-port-jdk17u/pull/28