RFR: 8347620: Shenandoah: Use 'free' tag for free set related logging [v3]

[William Kemper]

> Without a distinguishing tag, debug logging is too voluminous to enable when we really only want the free set's debug messages.

William Kemper has updated the pull request incrementally with one additional commit since the last revision:

  Fix merge mishap

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Changes:
  - all: https://git.openjdk.org/jdk/pull/23086/files
  - new: https://git.openjdk.org/jdk/pull/23086/files/6e04148c..2b613a82

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=23086&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=23086&range=01-02

  Stats: 4 lines in 1 file changed: 0 ins; 3 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/23086.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23086/head:pull/23086

PR: https://git.openjdk.org/jdk/pull/23086