Argobots state dump is very large

[roblatham00]

Argobots stack dump is helpful, or at least the human readable part is. I don't know who reads the 64k lines of raw data. There's a way to turn it off, though: pmodels/argobots#330 Margo should suppress the raw stack dump.

[carns]

I just realized that the env variable option must be set at margo init time (it is not re-evaluated at run time when collecting a stack trace). That's not terrific because it means that until we have an external function to set parameters (for use in ssg etc.) it will be hard to get consistent.

Leaving this open for now; when there is a new abt release and corresponding spack package update we can set the build-time option for this. When the general margo abt settings path is cleaned up a big (sort of in #118) we can try to standardize on setting the env variable.