`is_()` conditional methods should share their logic

[boonebgorges]

Many of the is_() methods in WP_Query share the nearly the exact same logic. As such, they share the exact same bugs, and fixing those bugs requires many parallel changes and huge numbers of tests. See #35902 and #24674 for some recent examples.

It's possible to move all the shared logic to a single protected utility method. It's a bit more abstract, but is much easier to maintain and test.

[boonebgorges]

35913.diff​ demonstrates how it can be done. (Look at all that red! <3)

The one slight functional change from the current behavior, made to simplify the new is_object_type(), is that *all* $object properties are cast to strings before the in_array() checks, instead of just the numerical ones. This will be redundant, since all of these properties are already strings.

Anyone have thoughts about the wisdom, or lack thereof, of this kind of abstraction?

[swissspidy]

I like the red!

Would be nice to see things move forward here.