Make tee work more nicely with non-collections (#13652)

# Description

This changes the behavior of `tee` to be more transparent when given a
value that isn't a list or range. Previously, anything that wasn't a
byte stream would converted to a list stream using the iterator
implementation, which led to some surprising results. Instead, now, if
the value is a string or binary, it will be treated the same way a byte
stream is, and the output of `tee` is a byte stream instead of the
original value. This is done so that we can synchronize with the other
thread on collect, and potentially capture any error produced by the
closure.

For values that can't be converted to streams, the closure is just run
with a clone of the value instead on another thread. Because we can't
wait for the other thread, there is no way to send an error back to the
original thread, so instead it's just written to stderr using
`report_error_new()`.

There are a couple of follow up edge cases I see where byte streams
aren't necessarily treated exactly the same way strings are, but this
should mostly be a good experience.

Fixes #13489.

# User-Facing Changes

Breaking change.

- `tee` now outputs and sends string/binary stream for string/binary
input.
- `tee` now outputs and sends the original value for any other input
other than lists/ranges.

# Tests + Formatting

Added for new behavior.

# After Submitting

- [ ] release notes: breaking change, command change

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

@@ -47,3 +47,23 @@ fn tee_save_stderr_to_file() {
         assert_eq!("teststring\n", file_contents(dirs.test().join("copy.txt")));
     })
 }
+
+#[test]
+fn tee_single_value_streamable() {
+    let actual = nu!("'Hello, world!' | tee { print -e } | print");
+    assert!(actual.status.success());
+    assert_eq!("Hello, world!", actual.out);
+    // FIXME: note the lack of newline: this is a consequence of converting the string to a stream
+    // for now, but most likely the printer should be checking whether a string stream ends with a
+    // newline and adding it unless no_newline is true
+    assert_eq!("Hello, world!", actual.err);
+}
+
+#[test]
+fn tee_single_value_non_streamable() {
+    // Non-streamable values don't have any synchronization point, so we have to wait.
+    let actual = nu!("500 | tee { print -e } | print; sleep 1sec");
+    assert!(actual.status.success());
+    assert_eq!("500", actual.out);
+    assert_eq!("500\n", actual.err);
+}