RFR: 8370807: G1: Improve region attribute table method naming

[Thomas Schatzl]

On Wed, 29 Oct 2025 11:09:18 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

>> It must be a region that is currently being added to the collection set. I.e. registered to the attribute table to be in the collection set.
>
> Then `in_cset` is a postcondition, not a precondition. The new name seems to suggest the arg (`r`) is old + in_cset, as a precondition.
> 
> Looking at the impl, one can't see anything related to "collection_set" in this context. I'd suggest restoring the original name, but YMMV.

The `set_in_old` call is the giveaway - in the region attribute table you only set a region to "Old" if it is 

  static const region_type_t Old          =   1;    // The region is in the collection set and an old region.

Old regions not in the collection set are just `NotInCset`.

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PR Review Comment: https://git.openjdk.org/jdk/pull/28038#discussion_r2472636224