SSE plugin: Speed up import

[gzotti]

Is your feature request related to a problem? Please describe.
Importing a large number of minor planets from MPC files, e.g. one of the 10.000 body lists, or "unusual objects", takes a long time.

Describe the solution you'd like
We have already improved loading time for OBJ files by applying from_chars(). Probably also parsing MPC files can be sped up. However, it may not be the original number parsing, but what follows.
Without fully going into the code, I fear we are parsing numbers, only to recreate string representations of the same numbers. It may be faster to keep the parsed numbers (strings identified as "containing numbers") as cropped strings (QStringView?) and putting them into the ssystem_minor.ini. Only substitute data that are not available from MPC files.

Describe alternatives you've considered
Waiting, having your favourite beverage...

Additional context
It is probably just a rarely used occasion to mass-load thousands of objects, so it's not a crucial thing, but a "nice-to-have". The SSE plugin UI can probably be improved in numerous other places.

[github-actions]

Hello @gzotti!

Thank you for suggesting this enhancement.