Add functionality for working with RECORD files

[SpecLad]

In pypa/pip#11762 I added some functionality for parsing/validating/serializing RECORD files. I thought about it some more, and it seems to me like that functionality belongs in this library. Would you be open to accepting something like this?

[brettcannon]

This ties into #697 , but I am not going to close this as a duplicate (yet) since we may want separate issues for each bit of wheel functionality we want to implement.

But do read that issue as it points out we are leaning towards doing a sans-I/O approach which means not doing any file I/O directly.

[SpecLad]

FWIW, RECORD files aren't just for wheels - they're also used in installed project metadata.

And I'm fine with not doing I/O directly, I can just make the API work with strings.

[jpmckinney]

I'm using importlib.metadata's distribution's files property for this, FWIW.