make sure new nul chars don't print in char --list (#15858)

# Description

This PR fixes and oversight. When we added `nul`, `null_byte`, and
`zero_byte` we forgot to make them non-printable for `char --list`.
That's what this PR fixes.

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crates/nu-command/src/strings/char_.rs

@@ -164,6 +164,9 @@ static NO_OUTPUT_CHARS: LazyLock<HashSet<&'static str>> = LazyLock::new(|| {
     [
         // If the character is in the this set, we don't output it to prevent
         // the broken of `char --list` command table format and alignment.
+        "nul",
+        "null_byte",
+        "zero_byte",
         "newline",
         "enter",
         "nl",