RFR: 8319703: Serial: Remove generationSpec

Wed Nov 8 10:59:34 UTC 2023

Simple cleanup of removing an unnecessary indirection. The real change is only 11 LOC, using the global variables directly for young/old gen.

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Commit messages:
 - s1-remove-gen-spec

Changes: https://git.openjdk.org/jdk/pull/16554/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16554&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8319703
  Stats: 265 lines in 12 files changed: 1 ins; 254 del; 10 mod
  Patch: https://git.openjdk.org/jdk/pull/16554.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16554/head:pull/16554

PR: https://git.openjdk.org/jdk/pull/16554