RFR: 8364532: G1: In liveness tracing, print more significant digits for the liveness value

[Thomas Schatzl]

Hi all,

  please review this small change that adds some more significant digits (3 in total) for the "liveness" column in collection set group logging.

E.g. see the emphasized columns that lack precision (it's more irritating with lots of lines showing single-digit values):

50.707s][trace][gc,liveness] GC(13) ### groud-id num-regions gc-eff liveness remset type
50.707s][trace][gc,liveness] GC(13) ### (bytes/ms) % (bytes)
50.707s][trace][gc,liveness] GC(13) ### 1 70       0.0 *100* 3199208 Y
50.707s][trace][gc,liveness] GC(13) ### 2 51 5298129.5  *18* 1224072 M
50.707s][trace][gc,liveness] GC(13) ### 3  5 3223983.6  *31*  176648 M
50.707s][trace][gc,liveness] GC(13) ### 4  5 3022016.3  *32*  176648 M


(This depends on PR#26591, so please look at that one first).

The change makes sure that three significant digits are printed.

Testing: manual review

Thanks,
  Thomas

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

Depends on: https://git.openjdk.org/jdk/pull/26591

Commit messages:
 - Merge branch '8364531-factor-out-liveness-code' into 8364532-liveness-significant-digits
 - * rename liveness() method to more accurate liveness_percent()
 - 8364532

Changes: https://git.openjdk.org/jdk/pull/26595/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=26595&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8364532
  Stats: 7 lines in 3 files changed: 1 ins; 1 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/26595.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26595/head:pull/26595

PR: https://git.openjdk.org/jdk/pull/26595