Deprecate the nu_scripts version of stdlib-candidate (#1042)

Deprecates the existing `stdlib-candidate` directories in `nu_scripts`
since `std-rfc` has now transitioned to the main repo. Updates readme
and renamed directories.

stdlib-candidate-archive/tests/path.nu

@@ -0,0 +1,39 @@
+use std-rfc/path
+use std/assert
+
+#[test]
+def path_with_extension [] {
+    let new_path = "ab.txt" | path with-extension "rs"
+    assert equal $new_path "ab.rs"
+
+    let new_path = "ab.txt" | path with-extension ".rs"
+    assert equal $new_path "ab.rs"
+}
+
+#[test]
+def path_with_extension_for_list [] {
+    let new_path = ["ab.txt", "cd.exe"] | path with-extension "rs"
+    assert equal $new_path ["ab.rs", "cd.rs"]
+
+
+    let new_path = ["ab.txt", "cd.exe"] | path with-extension ".rs"
+    assert equal $new_path ["ab.rs", "cd.rs"]
+}
+
+#[test]
+def path_with_stem [] {
+    let new_path = "/usr/bin" | path with-stem "share"
+    assert equal $new_path "/usr/share"
+
+    let new_path = ["/home/alice/", "/home/bob/secret.txt"] | path with-stem "nushell"
+    assert equal $new_path ["/home/nushell", "/home/bob/nushell.txt"]
+}
+
+#[test]
+def path_with_parent [] {
+    let new_path = "/etc/foobar" | path with-parent "/usr/share/"
+    assert equal $new_path "/usr/share/foobar"
+
+    let new_path = ["/home/rose/meow", "/home/fdncred/"] | path with-parent "/root/"
+    assert equal $new_path ["/root/meow", "/root/fdncred"]
+}