RFR: 8329603: G1: Merge G1BlockOffsetTablePart into G1BlockOffsetTable [v4]

[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 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 six additional commits since the last revision:

 - Merge branch 'master' into G1BlockOffsetTable
 - Move assert.
 - Remove unnecessary comments.
 - Fix indentation issue.
 - Use a simple/unified BOT.
 - JDK-8329603

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/18634/files
  - new: https://git.openjdk.org/jdk/pull/18634/files/a8a121bf..7db09f1d

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=18634&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=18634&range=02-03

  Stats: 11996 lines in 341 files changed: 4671 ins; 5622 del; 1703 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