Modifying offsets of existing members in _gc_runtime_state is probably a bad idea

[DinoV]

Bug report

Bug description:

The offset of _gc_runtime_state is exported via the debug offsets, but only offset within it is exported. It's likely that someone could be doing something slimey like looking at other fields. init. It's probably best to only add things to the end rather than change the offsets of existing members of the struct in a patch release.

CPython versions tested on:

3.14

Operating systems tested on:

No response

Linked PRs

• [3.14] gh-149242: Heap size should be added at end of the struct  #149241