Fix items spawning with fewer charges than defined in their item group entry

[ralreegorganon]

Summary

SUMMARY: Bugfixes "Fix items spawning with fewer charges than defined"

Purpose of change

An item spawn that looks like this { "item": "40x46mm_m1006", "charges": 4 } should spawn 4 charges of the item in question, but instead would spawn between 1 and 4 charges.

Per the documentation, defining charges like this should be setting the min and max charges to 4 (which it was), and then the actual spawn amount should be a random value between the min and max... which should be 4 (it wasn't).

I tracked this down to this change which effectively made it so that if the maximum charges was set (which happens both when setting the max directly or just setting the charges which sets both min and max) then the minimum number of charges would be set to 0 rather than the provided value. The system later clamps the minimum value to 1, thus resulting in a charges entry like "charges": x actually spawning between 1 and x charges.

Describe the solution

Wrote some unit tests to assert what I thought was happening here, confirmed that the particular scenario in question failed the test, then reverted the change and confirmed that all the tests passed.

Testing

The added unit tests.

[ZhilkinSerg]

Excel agrees:

variant	max_capacity	charges.first	charges.second	charges_min	charges_max	charges_min_f_pr	charges_min_f_prev	result_f_pr	result_f_prev
1	max_capacity	-1	-1	0	max_capacity	0	0	0-max_capacity	0-max_capacity
2	max_capacity	-1	second	0	second	0	0	0-second	0-second
3	max_capacity	first	-1	first	max_capacity	first	0	first-max_capacity	0-max_capacity
4	max_capacity	first	second	first	second	first	0	first-second	0-second