Msgpack commands (#12664)

# Description

I thought about bringing `nu_plugin_msgpack` in, but that is MPL with a
clause that prevents other licenses, so rather than adapt that code I
decided to take a crack at just doing it straight from `rmp` to `Value`
without any `rmpv` in the middle. It seems like it's probably faster,
though I can't say for sure how much with the plugin overhead.

@IanManske I started on a `Read` implementation for `RawStream` but just
specialized to `from msgpack` here, but I'm thinking after release maybe
we can polish it up and make it a real one. It works!

# User-Facing Changes
New commands:

- `from msgpack`
- `from msgpackz`
- `to msgpack`
- `to msgpackz`

# Tests + Formatting
Pretty thorough tests added for the format deserialization, with a
roundtrip for serialization. Some example tests too for both `from
msgpack` and `to msgpack`.

- 🟢 `toolkit fmt`
- 🟢 `toolkit clippy`
- 🟢 `toolkit test`
- 🟢 `toolkit test stdlib`


# After Submitting
- [ ] update release notes

crates/nu-test-support/src/macros.rs

@@ -245,6 +245,7 @@ use tempfile::tempdir;
 pub struct NuOpts {
     pub cwd: Option<String>,
     pub locale: Option<String>,
+    pub collapse_output: Option<bool>,
 }
 
 pub fn nu_run_test(opts: NuOpts, commands: impl AsRef<str>, with_std: bool) -> Outcome {
@@ -299,9 +300,15 @@ pub fn nu_run_test(opts: NuOpts, commands: impl AsRef<str>, with_std: bool) -> O
         .wait_with_output()
         .expect("couldn't read from stdout/stderr");
 
-    let out = collapse_output(&output.stdout);
+    let out = String::from_utf8_lossy(&output.stdout);
     let err = String::from_utf8_lossy(&output.stderr);
 
+    let out = if opts.collapse_output.unwrap_or(true) {
+        collapse_output(&out)
+    } else {
+        out.into_owned()
+    };
+
     println!("=== stderr\n{}", err);
 
     Outcome::new(out, err.into_owned(), output.status)
@@ -382,7 +389,7 @@ where
         .wait_with_output()
         .expect("couldn't read from stdout/stderr");
 
-    let out = collapse_output(&output.stdout);
+    let out = collapse_output(&String::from_utf8_lossy(&output.stdout));
     let err = String::from_utf8_lossy(&output.stderr);
 
     println!("=== stderr\n{}", err);
@@ -416,8 +423,7 @@ fn with_exe(name: &str) -> String {
     }
 }
 
-fn collapse_output(std: &[u8]) -> String {
-    let out = String::from_utf8_lossy(std);
+fn collapse_output(out: &str) -> String {
     let out = out.lines().collect::<Vec<_>>().join("\n");
     let out = out.replace("\r\n", "");
     out.replace('\n', "")