nu-path crate refactor (#3730)

* Resolve rebase artifacts

* Remove leftover dependencies on removed feature

* Remove unnecessary 'pub'

* Start taking notes and fooling around

* Split canonicalize to two versions; Add TODOs

One that takes `relative_to` and one that doesn't.
More TODO notes.

* Merge absolutize to and rename resolve_dots

* Add custom absolutize fn and use it in path expand

* Convert a couple of dunce::canonicalize to ours

* Update nu-path description

* Replace all canonicalize with nu-path version

* Remove leftover dunce dependencies

* Fix broken autocd with trailing slash

Trailing slash is preserved *only* in paths that do not contain "." or
"..". This should be fixed in the future to cover all paths but for now
it at least covers basic cases.

* Use dunce::canonicalize for canonicalizing

* Alow cd recovery from non-existent cwd

* Disable removed canonicalize functionality tests

Remove unused import

* Break down nu-path into separate modules

* Remove unused public imports

* Remove abundant cow mapping

* Fix clippy warning

* Reformulate old canonicalize tests to expand_path

They wouldn't work with the new canonicalize.

* Canonicalize also ~ and ndots; Unify path joining

Also, add doc comments in nu_path::expansions.

* Add comment

* Avoid expanding ndots if path is not valid UTF-8

With this change, no lossy path->string conversion should happen in the
nu-path crate.

* Fmt

* Slight expand_tilde refactor; Add doc comments

* Start nu-path integration tests

* Add tests TODO

* Fix docstring typo

* Fix some doc strings

* Add README for nu-path crate

* Add a couple of canonicalize tests

* Add nu-path integration tests

* Add trim trailing slashes tests

* Update nu-path dependency

* Remove unused import

* Regenerate lockfile

crates/nu-json/tests/main.rs

@@ -26,7 +26,7 @@ fn txt(text: &str) -> String {
 fn hjson_expectations() -> PathBuf {
     let assets = nu_test_support::fs::assets().join("nu_json");
 
-    dunce::canonicalize(assets.clone()).unwrap_or_else(|e| {
+    nu_path::canonicalize(assets.clone()).unwrap_or_else(|e| {
         panic!(
             "Couldn't canonicalize hjson assets path {}: {:?}",
             assets.display(),