RFR: 8286189 G1: Change "wasted" memory to "unused" memory in reporting

[Thomas Schatzl]

Hi all,

  please review this change of the term "wasted" to "unused" in memory reporting; "wasted" is a bit ambiguous, meaning memory that can't be used because it's blocked by something external (like the space at the end of humongous regions where gc needs to wait until the humongous objects is freed by the application).

Testing: gha

Thanks,
  Thomas

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Commit messages:
 - initial implementation

Changes: https://git.openjdk.java.net/jdk/pull/8550/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8550&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8286189
  Stats: 29 lines in 7 files changed: 2 ins; 0 del; 27 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8550.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8550/head:pull/8550

PR: https://git.openjdk.java.net/jdk/pull/8550