Better error handling

[madonuko]

In order to speed up development, we have been using color-eyre to conveniently handle errors in rpmspec-rs. This is of course poor practice and should be mitigated.

• Port all errors to thiserror #9
• Merge, separate and organize different errors as accordingly (in different categories)
• Absolutely phase out the use of color-eyre #10
• Include "span" and better position support for Consumer #12
• Use ariadne for traceback-like error messages #11

[dralley]

FYI, https://gitlab.com/cryptomilk/tree-sitter-rpmspec might be a source of inspiration on the parser design