RFR: 8305062: Refactor CardTable::resize_covered_region [v2]

[Albert Mingkun Yang]

> Simple refactoring to make logic around cardtable cover-region more concrete, since #generations and gen-boundary is fixed for Serial/Parallel.
> 
> Test: tier1-6

Albert Mingkun Yang has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last revision:

 - remove-committed
 - review
 - card-table-clear-memregion

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Changes:
  - all: https://git.openjdk.org/jdk/pull/13206/files
  - new: https://git.openjdk.org/jdk/pull/13206/files/4971107f..430acad6

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13206&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13206&range=00-01

  Stats: 265859 lines in 2361 files changed: 230589 ins; 21540 del; 13730 mod
  Patch: https://git.openjdk.org/jdk/pull/13206.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13206/head:pull/13206

PR: https://git.openjdk.org/jdk/pull/13206