RFR: 8331715: Remove virtual specifiers in ContiguousSpace

[Albert Mingkun Yang]

Trivial removing unused `virtual` and moving accessors together.

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Commit messages:
 - trivial

Changes: https://git.openjdk.org/jdk/pull/19099/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=19099&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8331715
  Stats: 9 lines in 1 file changed: 3 ins; 4 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/19099.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19099/head:pull/19099

PR: https://git.openjdk.org/jdk/pull/19099