RFR: 8327247: C2 uses up to 2GB of RAM to compile complex string concat in extreme cases

[Claes Redestad]

Splitting out the ASM-based version from #18690 to push that first under the JBS (to help backporting). Keeping #18690 open to rebase and follow-up on this as a subtask. See discussion in that #18690 for more details, discussion and motivation for this.

-------------

Commit messages:
 - Adapt main PR feedback to ASM version
 - ASM fallback version

Changes: https://git.openjdk.org/jdk/pull/18953/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18953&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8327247
  Stats: 300 lines in 2 files changed: 294 ins; 3 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/18953.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18953/head:pull/18953

PR: https://git.openjdk.org/jdk/pull/18953