Lots of tests for `emp::String` appear to be disabled

[mmore500]

See i.e.,

Empirical/tests/tools/String.cpp

Line 346 in fbf27dc

/*

We should check if these functions have been removed and, if not, if they are broken.

[mercere99]

emp::String was built in String.hpp based off of all of the functions in string_utils.hpp. I moved many of the string_util tests over, but some didn't apply cleanly. I do want to go through the rest more to see if any of them should be added, but I don't think it's critical. They weren't removed because of lack of passing or anything like that; they're still active in the string_utils.cpp tests.