RFR: 8318647: Serial: Refactor BlockOffsetTable

[Albert Mingkun Yang]

The diff is too large; maybe it's better to read the new impl directly, which I believe is much easier to follow.

There is some duplication with G1's implementation, which should probably be dealt with in its own PR.

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Commit messages:
 - s1-bot

Changes: https://git.openjdk.org/jdk/pull/16304/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16304&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8318647
  Stats: 791 lines in 8 files changed: 24 ins; 627 del; 140 mod
  Patch: https://git.openjdk.org/jdk/pull/16304.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16304/head:pull/16304

PR: https://git.openjdk.org/jdk/pull/16304