RFR: 8344263: GenShen: Reduce extraneous log messages at INFO level [v8]

[William Kemper]

> Genshen logs a lot of fine level detail at `gc=info`. This category should be reserved for major phase changes in the gc cycle.

William Kemper has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains eight additional commits since the last revision:

 - Merge remote-tracking branch 'shenandoah/master' into logging-cleanup
 - Fix old growth triggers test
 - Log all heuristic triggers with consistent formatting
 - Update test, remove unused header, use proper case for old gen phases
 - Fix formatting for non-generational log messages
 - Make generation names proper case
 - Log heuristics decisions at info with ergo tag
 - Reduce logging at info, use proper case for generation names

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

Changes:
  - all: https://git.openjdk.org/shenandoah/pull/540/files
  - new: https://git.openjdk.org/shenandoah/pull/540/files/02d3d24d..da70b543

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=shenandoah&pr=540&range=07
 - incr: https://webrevs.openjdk.org/?repo=shenandoah&pr=540&range=06-07

  Stats: 107288 lines in 2854 files changed: 28083 ins; 70210 del; 8995 mod
  Patch: https://git.openjdk.org/shenandoah/pull/540.diff
  Fetch: git fetch https://git.openjdk.org/shenandoah.git pull/540/head:pull/540

PR: https://git.openjdk.org/shenandoah/pull/540