Curried versions of endswith and startswith

[carstenbauer]

See discussion in #33193.

This PR adds single-argument versions endswith(s) and startswith(s) that return functions semantically equivalent to x->endswith(x,s) and x->startswith(x,s), respectively.

Example use case: filter(endswith(".toml"), readdir())

Closes #33193.

[fredrikekre]

Seems like just two test cases would cover everything?

[carstenbauer]

Seems like just two test cases would cover everything?

I started out with a definition of the curried versions including ::AbstractString annotations in which case Char support was lost. With these tests I want to make sure that whatever the definition of these curried variants is/will be in the future they should accept every type that the parent methods can handle.

In any case, the extra tests certainly don't hurt, do they?

[StefanKarpinski]

In any case, the extra tests certainly don't hurt, do they?

They don't in this case since they're fast and cheap to do but they will get run a lot.

[carstenbauer]

They don't in this case since they're fast and cheap to do but they will get run a lot.

Makes sense. I'll leave them as they are then unless someone objects.

[carstenbauer]

I've added a NEWS.md entry and compat annotations. (I also rebased onto master.)