Reduces false positives.
As an example:
result = "a" if TAINT else "c"
In AST, the assignment value is `IfExp(test=TAINT, body="a", orelse="c")`.
Even though `TAINT` is inside the assignment of `result`, it can't
actually taint `result` as it is part of the boolean test expression.
Previously, `result` would have been tainted, which was a false
positive.
We don't want to completely ignore the test though in case it contains a
sink function.
Therefore, if the test contains expressions we transform it as so:
result = "a" if b(c) + 2 else "d"
to the multi line:
__if_exp_0 = b(c) + 2
result = "a" if __if_exp_0 else "d"
This way if `b` is a sink and `c` is tainted we see a vulnerability, but
even if `c` is tainted we don't taint `result`.

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