Use path_isin instead of startswith to compare filepaths

[skshetry]

The PR #2798 introduced dvc.utils.fs.path_isin that can be used to compare child paths and parent paths and therefore, raw string compare with startswith can be replaced with this new function.

Refactor usage of startswith for paths with path_isin.

[skshetry]

@efiop, can I take this? If yes, please assign me. :)

[efiop]

@skshetry Sure, go ahead 🙂

[skshetry]

Looked through the codebase. The difference between path_isin and startswith is that, the former will be false if they are same path. The latter is being used here in the cases of where the path are same as well. Found 5/6 uses of startswith only.