This rule action accepts and assigns a set of 32 tags represented as a
32 bit integer just like all of river's other commands handling tags.
Using the singular here is potentially misleading and is also
inconsistent with set-view-tags, etc. which all use the plural.
Sorry about the breaking change for those who use master branch, ideally
I would have caught this before merging but at least I noticed before a
release.
This commit also does a bit of internal refactoring/cleanup of the rules
system.
c4fe1e1a3f