File system assertions

[epage]

So far, we only have file system fixture initialization and not file system assertions

Prior Art

• assert_cli and https://github.com/assert-rs/assert_cli/pull/98/commits
• cli_test_dir
• predicates::fs
• dir-diff + assert_dirs_eq = Expose a diffing iterator dir-diff#17

[epage]

We probably want a TempDir and ChildPath extension that accepts a path predicate and asserts.

Then we can leverage the path predicates that have implemented or are going to be implemented as part of https://github.com/assert-rs/predicates-rs/milestone/2

[epage]

To implement this, we probably want to wait on assert-rs/predicates-rs#30

[epage]

Fixed by 3ba02a9