RFR: 8338779: GenShen: Prefer log_develop_debug in performance critical code

[William Kemper]

There are a couple of places where the log level check is proportional to the number of oops being processed.

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Commit messages:
 - Fix whitespace
 - Use log_develop_debug in high traffic areas

Changes: https://git.openjdk.org/shenandoah/pull/481/files
  Webrev: https://webrevs.openjdk.org/?repo=shenandoah&pr=481&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8338779
  Stats: 5 lines in 2 files changed: 0 ins; 0 del; 5 mod
  Patch: https://git.openjdk.org/shenandoah/pull/481.diff
  Fetch: git fetch https://git.openjdk.org/shenandoah.git pull/481/head:pull/481

PR: https://git.openjdk.org/shenandoah/pull/481