fix(parser): reset stream position for direct string input, close #35

[Zhaoyilunnn]

Hi Team,

The root cause of #35 is as follows

https://github.com/openqasm/qe-qasm/blob/main/lib/Parser/QasmParser.y#L338-L342

Here IIS and ISS points to the same buffer, as std::getline moves the pointer to the next line, we got the wrong line number when directly parsing string.

Thus we just need to reset the position of IIS to make QASM::QasmPreprocessor::Instance().Preprocess(IIS) work as expected

I did not find any test codes in this repo to directly test QasmParser.y. I'm willing to add some tests and wish to know the proper way to do so.

Thanks,
Yilun

[taalexander]

This is tricky to test with the current test suite. We'll test next time we pull an updated version into the qe-compiler.