allow parse to work better with streams (#7870)

# Description

Fixes #7864. Haven't removed redundant code yet; and there's also a
weird visual bug, but I'm not sure if that's the fault of this PR or
just a quirk of how tabling works:

```
/home/gabriel/CodingProjects/nushell〉ping 1.1.1.1 | parse -r '(?P<num>\d+) ttl'                                                                                        01/27/2023 11:28:31 AM
╭───┬─────╮
│ # │ num │
├───┼─────┤
│ 0 │ 1   │
│ 1 │ 2   │
╰───┴─────╯
╭───┬─────╮
│ # │ num │
├───┼─────┤
│ 2 │ 3   │
╰───┴─────╯
╭───┬─────╮
│ # │ num │
├───┼─────┤
│ 3 │ 4   │
│ 4 │ 5   │
╰───┴─────╯
╭───┬─────╮
│ # │ num │
├───┼─────┤
│ 5 │ 6   │
│ 6 │ 7   │
╰───┴─────╯
^C
/home/gabriel/CodingProjects/nushell〉                                                                                                                                  01/27/2023 11:28:59 AM

```

# User-Facing Changes

_(List of all changes that impact the user experience here. This helps
us keep track of breaking changes.)_

# Tests + Formatting

Don't forget to add tests that cover your changes.

Make sure you've run and fixed any issues with these commands:

- `cargo fmt --all -- --check` to check standard code formatting (`cargo
fmt --all` applies these changes)
- `cargo clippy --workspace -- -D warnings -D clippy::unwrap_used -A
clippy::needless_collect` to check that you're using the standard code
style
- `cargo test --workspace` to check that all tests pass

# After Submitting

If your PR had any user-facing changes, update [the
documentation](https://github.com/nushell/nushell.github.io) after the
PR is merged, if necessary. This will help us keep the docs up to date.

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

@@ -189,4 +189,14 @@ mod regex {
                 .contains("Opening parenthesis without closing parenthesis"));
         })
     }
+
+    #[test]
+    fn parse_works_with_streaming() {
+        let actual = nu!(
+            cwd: ".", pipeline(
+               r#"seq char a z | each {|c| $c + " a"} | parse '{letter} {a}' | describe"#
+        ));
+
+        assert_eq!(actual.out, "table<letter: string, a: string> (stream)")
+    }
 }