RFR: 8306833: Change CardTable::_covered to static array

[Thomas Schatzl]

On Tue, 25 Apr 2023 10:30:49 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

> Simple refactoring to remove unused declaration in `vmStructs_gc.hpp`, which then enables more cleanup in `CardTable`.
> 
> Test: hotspot_gc

Marked as reviewed by tschatzl (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/13636#pullrequestreview-1399632849