refactor(prt): deconflict naming, use enum for tracking level

[wpbonelli]

Particle[Store]Type%idomain has nothing to do with discretization IDOMAIN, name it itrdomain for "tracking domain" to clarify what we mean. Also use an enum for method tracking level.

[wpbonelli]

This one can wait until after the release, since it sounds like we want to rethink where to define tracking level constants. Maybe introduce a base method type for each level, like we just did for cells in #2203?

[aprovost-usgs]

This one can wait until after the release, since it sounds like we want to rethink where to define tracking level constants. Maybe introduce a base method type for each level, like we just did for cells in #2203?

maybe that's a good approach - agree it can wait, and let's think on it some more. i'm generally wary of adding too many classes, but sometimes it just makes sense

[wpbonelli]

superseded