Cover all std functions in tests

[b1ek]

I don't like the current stdlib tests, because if it fails, it is very very hard to find out which function exactly has failed.

My proposal is to split that test into a lot of smaller ones and move them to a different file.

Also, as pointed out in https://github.com/Ph0enixKM/Amber/pull/114#issuecomment-2132228100, these tests do not cover some functions

[Ph0enixKM]

@b1ek tbh I wanted to do that too but didn't have time yet 😄