[jdk11u-dev] RFR: 8224624: Inefficiencies in CodeStrings::add_comment cause timeouts

[SendaoYan]

Hi all,
This is prefix backport of [JDK-8231058](https://bugs.openjdk.org/browse/JDK-8231058), after apply this backport will make backport of [JDK-8231058](https://bugs.openjdk.org/browse/JDK-8231058) cleanly.
This PR improves C1 compiled time of the test `compiler/c1/TestLinearScanOrderMain.java` method dramatically from 92s to 1.8s, and solve this test intermittent timeout.

Additonal testing:

- [ ] linux aarch64 build with release/slowdebug configure
- [ ] linux x86_64 build with release/slowdebug configure
- [ ] jtreg tests(include tier1/2/3 etc.) with release build on linux aarch64
- [ ] jtreg tests(include tier1/2/3 etc.) with release build on linux x86_64

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Commit messages:
 - 8224624: Inefficiencies in CodeStrings::add_comment cause timeouts

Changes: https://git.openjdk.org/jdk11u-dev/pull/2951/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=2951&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8224624
  Stats: 32 lines in 2 files changed: 23 ins; 3 del; 6 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/2951.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev.git pull/2951/head:pull/2951

PR: https://git.openjdk.org/jdk11u-dev/pull/2951