[jdk11u-dev] RFR: 8316906: Clarify TLABWasteTargetPercent flag

[Andrew Lu]

I backport this for parity with 11.0.22-oracle.

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Commit messages:
 - Backport 77fac0f4c6692bcc06456d03a4329d9f8ddeeded
 - Backport 77fac0f4c6692bcc06456d03a4329d9f8ddeeded

Changes: https://git.openjdk.org/jdk11u-dev/pull/2236/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=2236&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8316906
  Stats: 7 lines in 1 file changed: 5 ins; 2 del; 0 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/2236.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev.git pull/2236/head:pull/2236

PR: https://git.openjdk.org/jdk11u-dev/pull/2236