RFR: 8371625: G1: G1HeapRegion::print_on misalignment

[Ivan Walulya]

Hi,

Please review this fix to a misalignment in G1HeapRegion::print_on. Additionally, increased the field width for `hrm_index` as this also causes misalignment on large heaps.

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Commit messages:
 - fix

Changes: https://git.openjdk.org/jdk/pull/28229/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28229&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8371625
  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/28229.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28229/head:pull/28229

PR: https://git.openjdk.org/jdk/pull/28229