RFR: 8355300: Add final to BitSieve

[Shaojin Wen]

As the title says, adding final to fields that do not change and BitSieve that will not be inherited will make C2 optimization more friendly.

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Commit messages:
 - final

Changes: https://git.openjdk.org/jdk/pull/24796/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=24796&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8355300
  Stats: 5 lines in 1 file changed: 0 ins; 0 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/24796.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24796/head:pull/24796

PR: https://git.openjdk.org/jdk/pull/24796