Make into bits produce bitstring stream (#13310)

# Description

Fix `into bits` to have consistent behavior when passed a byte stream.

# User-Facing Changes

Previously, it was returning a binary on stream, even though its
input/output types don't describe this possibility. We don't need this
since we have `into binary` anyway.

# Tests + Formatting
Tests added

crates/nu-cmd-extra/tests/commands/bits/into.rs

@@ -0,0 +1,13 @@
+use nu_test_support::nu;
+
+#[test]
+fn byte_stream_into_bits() {
+    let result = nu!("[0x[01] 0x[02 03]] | bytes collect | into bits");
+    assert_eq!("00000001 00000010 00000011", result.out);
+}
+
+#[test]
+fn byte_stream_into_bits_is_stream() {
+    let result = nu!("[0x[01] 0x[02 03]] | bytes collect | into bits | describe");
+    assert_eq!("string (stream)", result.out);
+}

crates/nu-cmd-extra/tests/commands/bits/mod.rs

@@ -0,0 +1 @@
+mod into;