a version of getDataFileName that uses OsPath

**Describe the feature request**

Cabal has the feature to generate a Paths_ module that exports utility functions to access data files; for example, it generates a 'getDataFileName :: FilePath -> IO FilePath' function that given a fileName/local filePath constructs the correct absolute path to the file in the data-directory set in the cabal file. See https://cabal.readthedocs.io/en/stable/cabal-package-description-file.html#accessing-data-files-from-package-code for details.

It would be nice if cabal could generate a similar functions that use OsPath rather than FilePath; since OsPath provides a better/more compact encoding of file paths. Perhaps it would be cleanest if cabal would actually generate a separate module (e.g. OsPaths_) that has the OsPath versions.

Start with Cabal's generated Paths_ module and the existing getDataFileName function described in the linked data-files documentation. Investigate how the generated module is specified and whether a separate OsPaths_ module is appropriate. Done means Cabal generates usable OsPath-based data-file accessors for packages that request the feature.

Written by the indexing model from the issue text.