Tagged release v3.31.0

8766155 fix(ALE,CSE,CSD): percentage definition from value with tax issue: https://gitlab.prozorro.sale/prozorro-sale/billing/-/issues/93
a144d6f fix(SPD,SPE): return 0 if finalValueSum negative https://gitlab.prozorro.sale/prozorro-sale/billing/-/issues/95
d444dd7 test: add tests for the remaining procedures
6675ae6 test(BRE): add test for operatorFee variable
696ccba test(ALE): add test for operatorFee calculation
0c0093c test: add fixtures
adef902 test: check operatorFee, operatorToBidderSum dependence on schedule value