RFR: 8314274: G1: Fix -Wconversion warnings around G1CardSetArray::_data

Tue Aug 15 13:34:28 UTC 2023

Add value-range check and explicit type conversion. The second write has its check at the beginning of the method, so doesn't require an assertion.

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Commit messages:
 - g1-remset-data

Changes: https://git.openjdk.org/jdk/pull/15289/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15289&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8314274
  Stats: 3 lines in 1 file changed: 1 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/15289.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15289/head:pull/15289

PR: https://git.openjdk.org/jdk/pull/15289