RFR: JDK-8305320: DbgStrings and AsmRemarks are leaking

[Justin King]

Fix two leaks related to `DbgStrings` and `AsmRemarks` in debug builds.

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Commit messages:
 - Fix leaks related to AsmRemarks and DbgStrings
 - Revert "Fix leak related to DbgStrings"
 - Fix leak related to DbgStrings

Changes: https://git.openjdk.org/jdk/pull/13249/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13249&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8305320
  Stats: 9 lines in 3 files changed: 9 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/13249.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13249/head:pull/13249

PR: https://git.openjdk.org/jdk/pull/13249