RFR: 8329603: G1: Merge G1BlockOffsetTablePart into G1BlockOffsetTable [v2]

[Guoxiong Li]

> Hi all,
> 
> This patch merges `G1BlockOffsetTablePart` into `G1BlockOffsetTable`. The previous fields `_reserved` and `_offset_base` of `G1BlockOffsetTable` are marked as `static` so that they can be shared by BOTs of all the heap regions.
> 
> The tests `make test-tier1_gc` passed locally. Thanks for taking the time to review.
> 
> Best Regards,
> -- Guoxiong

Guoxiong Li has updated the pull request incrementally with one additional commit since the last revision:

  Use a simple/unified BOT.

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/18634/files
  - new: https://git.openjdk.org/jdk/pull/18634/files/e167a24f..ccafb2f7

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=18634&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=18634&range=00-01

  Stats: 89 lines in 8 files changed: 10 ins; 41 del; 38 mod
  Patch: https://git.openjdk.org/jdk/pull/18634.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18634/head:pull/18634

PR: https://git.openjdk.org/jdk/pull/18634