Assert with the PyStackRef_IsTaggedInt function

[nybblista]

In the _PyStackRef_AsPyObjectBorrow, I think we should use the PyStackRef_IsTaggedInt rather than asserting the ref.index value directly from the function. However, the same thing applies to the PyStackRef_UntagInt function, which asserts the i.bits value rather than calling the PyStackRef_IsTaggedInt function.

Linked PRs

• gh-133476: Assert with the PyStackRef_IsTaggedInt function #133477