`vm_setinstancevariable` had a codepath to try to match the inline
cache for types other than T_OBJECT, but the cache population path
in `vm_setivar_slowpath` was exclusive to T_OBJECT, so `vm_setivar_default`
would never match anything.
This commit improves `vm_setivar_slowpath` so that it is capable of
filling the cache for all types, and adds a `vm_setivar_class` codepath
for `T_CLASS` and `T_MODULE`.
`vm_setivar`, `vm_setivar_default` and `vm_setivar_class` could be unified,
but based on the very explicit `NOINLINE` I assume they were split to minimize
codesize.
```
compare-ruby: ruby 3.5.0dev (2025-08-27T14:58:58Z merge-vm-setivar-d.. 5b749d8e53) +PRISM [arm64-darwin24]
built-ruby: ruby 3.5.0dev (2025-08-27T16:30:31Z setivar-cache-gene.. 4fe78ff296) +PRISM [arm64-darwin24]
| |compare-ruby|built-ruby|
|:------------------------|-----------:|---------:|
|vm_ivar_set_on_instance | 161.809| 164.688|
| | -| 1.02x|
|vm_ivar_set_on_generic | 58.769| 115.638|
| | -| 1.97x|
|vm_ivar_set_on_class | 70.034| 141.042|
| | -| 2.01x|
```