[class.temporary] Clarify that list of contexts is exhaustive

[eisenwave]

Fixes NB US 19-037 (C++26 CD).
Fixes cplusplus/nbballot#612.

We used to say "five" in this place before applying cplusplus/papers#156, which replaced that with "several" because updating the counter each time is a bit silly.

However, this does lose the clarity that the list of lifetime extension contexts in [class.temporary] is exhaustive, so we need to add something like "all listed below" if don't want a counter but clearly have an exhaustive list.

[jwakely]

The sentence seems a bit clunky now, after a series of micro-changes. How about a bigger change that (I think) improves it:

Temporaries are destroyed at a different point than the end of the full-expression in the following contexts:

[eisenwave]

@jwakely that sounds less clunky. I've used that wording except that I've replaced "temporaries" with "temporary objects". To my knowledge, the former is a colloquialism.