Update Yecc backend to parse unicode strings

[ejschmitt]

I wanted to parse unicode string values with the Yecc backend, so added this change.

I'm not super familiar with the differences between :erlang.iolist_to_binary() vs :unicode.characters_to_binary(), so maybe it's not this easy?
Not sure, but hey, the tests pass 🤷

[thomas9911]

I think indeed I used :erlang.iolist_to_binary() to convert from a list to a binary. If the other function does that as well + supports unicode. That sounds good to me 👌

[thomas9911]

I fixed the github pipelines can you merge main into your branch?

[ejschmitt]

Updated with master. The test updates for otp 26+ look good, I didn't want to change a bunch of stuff since I don't know the repo well. Thanks!