Insert SortTrackAction when sorting by particle type

[esseivaju]

I didn't update the switch statement which is inserting the SortTracksAction in #1044.

Also refactoring CoreState to only have the necessary thread_offsets_ collection, moving all the template code to the internal state struct CoreStateThreadOffsets.

[sethrj]

Changing the "default" to spelling out the remaining options would be safer since clang will catch the omission.

[esseivaju]

yes, I was considering doing that (or using pragma diagnostic switch-enum?) but given that we do a switch on that enum in many places and it's not likely to get updated often, I ended up leaving the default. Maybe just doing it in accel is fine since it's not closely related to SortTracksAction you're more likely to forget it here.

[sethrj]

For some reason github isn't letting me code review. Two comments:

1. Can you add a super small test to TrackSort.test.cc that fails before the fix and passes after? (maybe we need something more "manual" than running a whole tracking loop? i.e. something to fill up some bogus states and just launch the action)
2. Does is_sort_by_action in SortTracksAction.cc also need to be updated? If so maybe it needs to be rephrased by negating the enums that don't need sorting.

[esseivaju]

1. Can you add a super small test to TrackSort.test.cc that fails before the fix and passes after? (maybe we need something more "manual" than running a whole tracking loop? i.e. something to fill up some bogus states and just launch the action)

Mmh, how would you test that? You have to instantiate CoreParams and check that it is in the expected state given its input. Wouldn't that fit better in a dedicated CoreParams unit test?

2. Does is_sort_by_action in SortTracksAction.cc also need to be updated? If so maybe it needs to be rephrased by negating the enums that don't need sorting.

This doesn't need to be updated. This is used when sorting on a key that would allow to launch a kernel with a reduced grid size. This is not the case for particle_type.

[sethrj]

TrackSort.test.cc already does create core instances. You could manually call the initialize track action to set a bunch of primaries, then just manually call the sort action, then check that the order is correct?

[sethrj]

Nice improvement. Thanks for figuring out a way to add the tests!