Replace the old encode base64 and decode base64 with new-base64 commands (#14018)

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# Description
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Maybe we can deprecate `encode new-base64` and `decode new-base64`
first, to make the code clean and simple I'd rather remove the old
`encode base64` and `decode base64` and replace them with the `*
new-base64` commands.

Related PR: https://github.com/nushell/nushell/pull/13428

# User-Facing Changes
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helps us keep track of breaking changes. -->

- `encode new-base64` --> `encode base64`
- `decode new-base64` --> `decode base64`

# Tests + Formatting
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It's a breaking change

crates/nu-command/tests/commands/hash_/mod.rs

@@ -10,43 +10,48 @@ fn base64_defaults_to_encoding_with_standard_character_type() {
 }
 
 #[test]
-fn base64_encode_characterset_binhex() {
+fn base64_defaults_to_encoding_with_nopad() {
     let actual = nu!(r#"
-        echo 'username:password' | encode base64 --character-set binhex
+        echo 'username:password' | encode base64 --nopad
         "#);
 
-    assert_eq!(actual.out, "GA0PFQjKE@8kF'&cFhG[FQ3");
+    assert_eq!(actual.out, "dXNlcm5hbWU6cGFzc3dvcmQ");
 }
 
 #[test]
-fn error_when_invalid_character_set_given() {
+fn base64_decode_value() {
     let actual = nu!(r#"
-        echo 'username:password' | encode base64 --character-set 'this is invalid'
+        echo 'YWJjeHl6' | decode base64 | decode
         "#);
 
-    assert!(actual
-        .err
-        .contains("this is invalid is not a valid character-set"));
+    assert_eq!(actual.out, "abcxyz");
 }
 
 #[test]
-fn base64_decode_characterset_binhex() {
-    let actual = nu!(
-        r#""GA0PFQjKE@8kF'&cFhG[FQ3" | decode base64 --character-set binhex --binary | decode utf-8"#
-    );
+fn base64_decode_with_nopad() {
+    let actual = nu!(r#"
+        echo 'R29vZCBsdWNrIHRvIHlvdQ' | decode base64 --nopad | decode
+        "#);
 
-    assert_eq!(actual.out, "username:password");
+    assert_eq!(actual.out, "Good luck to you");
+}
+
+#[test]
+fn base64_decode_with_url() {
+    let actual = nu!(r#"
+        echo 'vu7_' | decode base64 --url | decode
+        "#);
+
+    assert_eq!(actual.out, "¾îÿ");
 }
 
 #[test]
 fn error_invalid_decode_value() {
     let actual = nu!(r#"
-        echo "this should not be a valid encoded value" | decode base64 --character-set url-safe
+        echo "this should not be a valid encoded value" | decode base64
         "#);
 
-    assert!(actual
-        .err
-        .contains("invalid base64 input for character set url-safe"));
+    assert!(actual.err.contains("nu::shell::incorrect_value"));
 }
 
 #[test]