scale testing: run scaletests in nightly-gauntlet

[ammario]

A request for @johnstcn:

It would be very helpful to have a job in the nightly-gauntlet workflow that performs an aggressive scaletest and fails if any error occurs. We can then learn about performance regressions or scale bugs day-of.

[bpmct]

I'm working on an RFC to run a bunch of tests weekly (scale, networking, performance). Going to close this out for now