RFR: 8303824: Parallel: Use more strict card table API

[Albert Mingkun Yang]

Simple refactoring to update only cards of committed heap.

Test: tier1-3

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Commit messages:
 - card-table-memregion

Changes: https://git.openjdk.org/jdk/pull/12928/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12928&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8303824
  Stats: 8 lines in 2 files changed: 5 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/12928.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12928/head:pull/12928

PR: https://git.openjdk.org/jdk/pull/12928