RFR: 8289538: Make G1BlockOffsetTablePart unaware of block sizes [v3]

[Thomas Schatzl]

> Hi all,
> 
>   can I have reviews for this change that makes `G1BlockOffsetTablePart` unaware of block sizes: as discussed in PR#9059/[JDK-8287555](https://bugs.openjdk.org/browse/JDK-8287555) this is a good idea to make `G1BlockOffsetTablePart` just for "dumb" retrieval of the BOT entries, which makes the code simpler, avoiding some calling back and forth between `HeapRegion` and `G1BlockOffsetTablePart`.
> 
> There is still the wart that `G1BlockOffsetTablePart::verify()` needs `block_size`, but since it's just verification I think this is fine. An alternative suggested by @albertnetymk is to remove that method completely.
> 
> Testing: local compilation, gha, some benchmark checking that card scans/ms does not degrade
> 
> Thanks,
>   Thomas

Thomas Schatzl has updated the pull request incrementally with two additional commits since the last revision:

 - ayang review
 - cleanup

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/9395/files
  - new: https://git.openjdk.org/jdk/pull/9395/files/9e847fc0..5eddae0a

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=9395&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=9395&range=01-02

  Stats: 26 lines in 5 files changed: 6 ins; 15 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/9395.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9395/head:pull/9395

PR: https://git.openjdk.org/jdk/pull/9395