Excessive newlines in printing ASR expression

Original issue: https://gitlab.com/lfortran/lfortran/-/issues/110

Attempting to convert a directly constructed LFortran ASR object to source code
prints an excessive number of newlines in the resulting expression:

>>> integer = lfortran.asr.builder.make_type_integer()
>>> a = lfortran.asr.asr.Variable(name="a", type=integer)
>>> b = lfortran.asr.asr.Variable(name="b", type=integer)
>>> expr = lfortran.asr.builder.make_binop(a, lfortran.asr.asr.Add(), b)
>>> lfortran.ast_to_src(lfortran.asr_to_ast(expr))
'a\n \n+\n \nb\n'

I'm not sure whether this is the right way to print the resulting string (that's
at least how its done in the builder test, though it's applied to an entire
module).

I'm currently using LFortran 0.1.14, distributed by PyPI.

Start with the lfortran.asr.builder and the asr_to_ast and ast_to_src entry points used in the reproduction, then compare them with the builder test mentioned in the issue. Verify how a directly constructed binary expression is converted and printed; done means the expression no longer contains unexplained extra newlines.