MOCK: Modify NUMERIC-type macros to operate natively with negative/float values too

[orandb]

We used STAT_ADD_NUMERIC_MOCK to mock a variable that is from float type.
For some reason, we didn't get the correct value.
after a debug session, we saw that the converting from float to unsign was incorrect, and required the same method like in STAT_ADD_MOCK when the value is copied as void.