GsimRupture initialized for each magnitude (new smtk) vs only once (old smtk)

[rizac]

Tests of Trellis vs magnitude do not produce the same results as in old smtk. Reason is that for each magnitude we initialize now a new Gsimrupture, whereas in the old code it seem that we initialized only one rupture for all magnitudes:

https://github.com/GEMScienceTools/gmpe-smtk/blob/7948682b32ef804a52d266dfcc94512da01149ab/smtk/trellis/trellis_plots.py#L434C9-L439C61

The behavior looks right in the new version and a bug in the old one, but I need confirmation for this
(@g-weatherill no need to reply here, we'll discuss in the next days)