Finished my D-Bus interface rework. Updated the MR description with the planned actual commit message. Sorry it got large - almost all of the originally introduced code is touched in some way, though simple renames take up most of the diff.
Please review and point out any shortcomings. (I included the transformation of the extra "configured to suppress" boolean to uint flags as a fixup, in case this part is controversial. No history is available for reverting any other controversies.)
I think it would pay off to also include a replacement for the HasInhibition() call likewise with a systemd-style property (BlockInhibited) that includes "sleep:idle" blocking policies. But that can come later in a separate MR, it's not related to any of the suppressed inhibition APIs from !363 (merged).
(I don't think it makes sense to also replace AddInhibition(), ReleaseInhibition() - clients should just use the portals API anyway. I guess we could still mark these methods as deprecated and point to portals.)