RFR: 8290223: Initialize G1CardClosure in card scanning once

[Thomas Schatzl]

Hi all,

  please review this minor change to avoid repeatedly initializing `G1CardClosure` in card scanning.

Testing: gha, local compilation

Thanks,
  Thomas

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Commit messages:
 - initial version

Changes: https://git.openjdk.org/jdk/pull/9478/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=9478&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8290223
  Stats: 5 lines in 1 file changed: 3 ins; 1 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/9478.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9478/head:pull/9478

PR: https://git.openjdk.org/jdk/pull/9478