RFR: 8328573: Add ASSERT macro and not use 'CardTable::card_shift_in_words' in 'G1BlockOffsetTable::check_index'

[Guoxiong Li]

Hi all,

This patch adds the ASSERT macro to the declaration and usages of the method `G1BlockOffsetTable::check_index`. And the `CardTable::card_shift_in_words` is changed to `CardTable::card_shift` in order to prepare [JDK-8328508](https://bugs.openjdk.org/browse/JDK-8328508).

Thanks for taking the time to review.

Best Regards,
-- Guoxiong

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Commit messages:
 - Add ASSERT macro and don't use CardTable::card_shift_in_words.

Changes: https://git.openjdk.org/jdk/pull/18391/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18391&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8328573
  Stats: 16 lines in 3 files changed: 14 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/18391.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18391/head:pull/18391

PR: https://git.openjdk.org/jdk/pull/18391