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/std-rfc/conversions/record-into-columns.nu

@@ -0,0 +1,34 @@
+# Convert a record, where each value is a list, into a list of columns.
+# { a: [ 1 2 3 ], b: [ 4 5 6 ] } | record-into-columns
+# => ╭───┬───────────╮
+# => │ 0 │ ╭───┬───╮ │
+# => │   │ │ # │ a │ │
+# => │   │ ├───┼───┤ │
+# => │   │ │ 0 │ 1 │ │
+# => │   │ │ 1 │ 2 │ │
+# => │   │ │ 2 │ 3 │ │
+# => │   │ ╰───┴───╯ │
+# => │ 1 │ ╭───┬───╮ │
+# => │   │ │ # │ b │ │
+# => │   │ ├───┼───┤ │
+# => │   │ │ 0 │ 4 │ │
+# => │   │ │ 1 │ 5 │ │
+# => │   │ │ 2 │ 6 │ │
+# => │   │ ╰───┴───╯ │
+# => ╰───┴───────────╯
+# =>
+# This can be especially useful when combined with `columns-into-table`, as in:
+#
+# { a: [ 1 2 3 ], b: [ 4 5 6 ] } | record-into-columns
+# | columns-into-table
+# => ╭───┬───┬───╮
+# => │ # │ a │ b │
+# => ├───┼───┼───┤
+# => │ 0 │ 1 │ 4 │
+# => │ 1 │ 2 │ 5 │
+# => │ 2 │ 3 │ 6 │
+# => ╰───┴───┴───╯
+# =>
+export def main []: [record -> list] {
+    items {|key, val| $val | wrap $key}
+}