Fragile and Sturdy flags cannot be inherited

[John-Candlebury]

Summary

Bugfixes "Fragile and Sturdy flags cannot be inherited"

Purpose of change

Fixes: #75163

And overall it doesnt make sense for the base item to ever become fragile/sturdy when you attach items to it.

[Karol1223]

I do not see why limiting the compatibility of the flags with copy-from is the way to go instead of solving the problem where it actually is a problem through the use of delete syntax.

[Procyonae]

You could potentially make it so that extending with sturdy/fragile removes the other (or some general form of that for conflicting flags) would be fine but just removing inheritance from stuff isn't cool

[John-Candlebury]

Oh this affects only the behaviour of the "inherits_flags" pocket setting, as when you mount a NVG unit to an army helmet. "copy-from" functionality wont be affected by this.

[RedMisao]

Modded the inherit line to check if a item B being a copy-from item A with FRAGILE inherited the flag, and it does.
Most importantly, it is already documented to work for attachments/pockets, my bad.

[John-Candlebury]

No worries.