The zip command. (#3919)

We introduce it here and allow it to work with regular lists (tables with no columns) as well as symmetric tables. Say we have two lists and wish to zip them, like so:

```
[0 2 4 6 8] | zip {
  [1 3 5 7 9]
} | flatten

───┬───
 0 │ 0
 1 │ 1
 2 │ 2
 3 │ 3
 4 │ 4
 5 │ 5
 6 │ 6
 7 │ 7
 8 │ 8
 9 │ 9
───┴───
```

In the case for two tables instead:

```
[[symbol]; ['('] ['['] ['{']] | zip {
  [[symbol]; [')'] [']'] ['}']]
} | each {
  get symbol | $'($in.0)nushell($in.1)'
}

───┬───────────
 0 │ (nushell)
 1 │ [nushell]
 2 │ {nushell}
───┴───────────
```

crates/nu-command/tests/commands/mod.rs

@@ -63,3 +63,4 @@ mod where_;
 mod which;
 mod with_env;
 mod wrap;
+mod zip;

crates/nu-command/tests/commands/zip.rs

@@ -0,0 +1,77 @@
+use nu_test_support::fs::Stub::FileWithContent;
+use nu_test_support::pipeline as input;
+use nu_test_support::playground::{says, Playground};
+
+use hamcrest2::assert_that;
+use hamcrest2::prelude::*;
+
+const ZIP_POWERED_TEST_ASSERTION_SCRIPT: &str = r#"
+def expect [
+    left,
+    right,
+    --to-eq
+] {
+    $left | zip { $right } | all? {
+        $it.name.0 == $it.name.1 && $it.commits.0 == $it.commits.1
+    }
+}
+
+def add-commits [n] {
+  each {
+    let contributor = $it;
+    let name = $it.name;
+    let commits = $it.commits;
+
+    $contributor | merge {
+      [[commits]; [($commits + $n)]]
+    }
+  }
+}
+"#;
+
+#[test]
+fn zips_two_tables() {
+    Playground::setup("zip_test_1", |dirs, nu| {
+        nu.with_files(vec![FileWithContent(
+            "zip_test.nu",
+            &format!("{}\n", ZIP_POWERED_TEST_ASSERTION_SCRIPT),
+        )]);
+
+        assert_that!(
+            nu.pipeline(&input(&format!(
+                r#"
+                source {} ;
+        
+                let contributors = ([
+                  [name, commits];
+                  [andres,    10]
+                  [    jt,    20]
+                ]);
+                        
+                let actual = ($contributors | add-commits 10);
+                        
+                expect $actual --to-eq [[name, commits]; [andres, 20] [jt, 30]]
+                "#,
+                dirs.test().join("zip_test.nu").display()
+            ))),
+            says().stdout("true")
+        );
+    })
+}
+
+#[test]
+fn zips_two_lists() {
+    Playground::setup("zip_test_2", |_, nu| {
+        assert_that!(
+            nu.pipeline(&input(
+                r#"
+                echo [0 2 4 6 8] | zip { [1 3 5 7 9] }
+                | flatten
+                | into string
+                | str collect '-'
+                "#
+            )),
+            says().stdout("0-1-2-3-4-5-6-7-8-9")
+        );
+    })
+}