nu-cli refactor moving commands into their own crate nu-command (#2910)

* move commands, futures.rs, script.rs, utils

* move over maybe_print_errors

* add nu_command crate references to nu_cli

* in commands.rs open up to pub mod from pub(crate)

* nu-cli, nu-command, and nu tests are now passing

* cargo fmt

* clean up nu-cli/src/prelude.rs

* code cleanup

* for some reason lex.rs was not formatted, may be causing my error

* remove mod completion from lib.rs which was not being used along with quickcheck macros

* add in allow unused imports

* comment out one failing external test; comment out one failing internal test

* revert commenting out failing tests; something else might be going on; someone with a windows machine should check and see what is going on with these failing windows tests

* Update Cargo.toml

Extend the optional features to nu-command

Co-authored-by: Jonathan Turner <jonathandturner@users.noreply.github.com>

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

@@ -0,0 +1,31 @@
+use nu_test_support::nu;
+use nu_test_support::playground::Playground;
+
+#[test]
+fn creates_a_file_when_it_doesnt_exist() {
+    Playground::setup("create_test_1", |dirs, _sandbox| {
+        nu!(
+            cwd: dirs.test(),
+            "touch i_will_be_created.txt"
+        );
+
+        let path = dirs.test().join("i_will_be_created.txt");
+        assert!(path.exists());
+    })
+}
+
+#[test]
+fn creates_two_files() {
+    Playground::setup("create_test_2", |dirs, _sandbox| {
+        nu!(
+            cwd: dirs.test(),
+            "touch a b"
+        );
+
+        let path = dirs.test().join("a");
+        assert!(path.exists());
+
+        let path2 = dirs.test().join("b");
+        assert!(path2.exists());
+    })
+}