RFR: 8371381: [Shenandoah] Setting ergo flags should use FLAG_SET_ERGO

[Rui Li]

Setting ergo flags using `FLAG_SET_ERGO`, instead of `FLAG_SET_DEFAULT`, so we can have the right origin info.

Had to expand `ShenandoahEvacReserve` range from `range(1,100)` to `range(0,100)` because when we use shenandoah passive mode and degen is also turned off (`-XX:ShenandoahGCMode=passive -XX:-ShenandoahDegeneratedGC`), we set the ShenandoahEvacReserve to 0:  https://github.com/openjdk/jdk/blob/c6a8027b94bbcbde5f7dcabd0bff48b93bbb5a7f/src/hotspot/share/gc/shenandoah/mode/shenandoahPassiveMode.cpp#L41 The issue is surfaced now because `FLAG_SET_DEFAULT` doesn't check the range but `FLAG_SET_ERGO` does.

Testing: jtreg gc. GHA pending.

-------------

Commit messages:
 - 8371381: [Shenandoah] Setting ergo flags should use FLAG_SET_ERGO

Changes: https://git.openjdk.org/jdk/pull/28242/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28242&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8371381
  Stats: 4 lines in 2 files changed: 0 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/28242.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28242/head:pull/28242

PR: https://git.openjdk.org/jdk/pull/28242