Add proper instances support with shared instance settings

[dimitarsp]

Is your feature request related to a problem? Please describe.
Prusa Slicer has simple and straightforward instancing that to my understanding has been commented out of the code in Bambu Studio because it is "too complicated" (comments from devs on other posts). But setting the same parameters and adjustments to multiple duplicates is unnecessary and time consuming. If we have proper instances then, those settings can easily be shared.

Describe the solution you'd like
Add instances support as in Prusa Slicer

For reference, it is also being looked into in Orca Slicer SoftFever/OrcaSlicer#6237