Implement out_of_page setting like D7 module.

Let's see if a small tweak gets the tests to pass.

Let's now resolve most coding standards issues (only one left is to prevent a merge conflict with 2905038 #7).

Looks like Simpletest tests got broken by an incomplete refactor of a method name.

And to round it all, let's also add a simple assert for out_of_page slots; for simplicity, I just leveraged the existing Simpletest test... better to work on converting those into PHPUnit in a separate issue.

Ready for review; context integration is to be done at #3116001: Context integration (out-of-page slots) (once the work here is finished and merged).

Just undoing a coding-standards fix, in order to get this patch to apply cleanly on top of #2905038: Add back token browser #7.

Just attaching a version of #13 that can be applied on top of 2d0d5a3 + #2905298: Javascript outdated #15, should anybody want the proper async/sync switching alongside out-of-page support.

Re-rolling #13 for DFP 1.0, without the test. It also applies on top of DFP 1.0 + #2905298: Javascript outdated #17.

TODO:

- Port the test from #13.

Re-rolling #15 for DFP 1.2.

It also applies on top of DFP 1.2 + #2905298-22: Javascript outdated.

No interdiff; the only conflict I had to resolve manually was that |raw was used in the twig file before DFP 1.2, but now it isn't.

TODO:

- Port test from #13.

Tests are unstable; see #3280781: Stabilize tests for D9.3.

Thank for contributing!
Can we create merge request for 2.0.x branch?

Setting to NR.

I just created MR 25, since MR 22 was set to merge onto 8.x-1.x and I couldn't find a way to switch it to merge into 2.0.x.

I'm also attaching the patch from current MR 25, which applies cleanly on top of 2.0.2.

Needs a rebase