[refactoring] Group all the CBOR util functions in cbor_util

This cl only moves all the CBOR utility functions in one place.
Some return error types are adjusted to adapt the change. There
should be no behavior change.

Bug: 310931749
Test: atest rialto_test
Change-Id: Ie3db9c93b1355d25d7d796818e19e554560e1f23
diff --git a/libs/bssl/src/ec_key.rs b/libs/bssl/src/ec_key.rs
index 0c944cd..894934d 100644
--- a/libs/bssl/src/ec_key.rs
+++ b/libs/bssl/src/ec_key.rs
@@ -17,9 +17,7 @@
 
 use crate::cbb::CbbFixed;
 use crate::cbs::Cbs;
-use crate::util::{
-    check_int_result, get_label_value, get_label_value_as_bytes, to_call_failed_error,
-};
+use crate::util::{check_int_result, to_call_failed_error};
 use alloc::vec;
 use alloc::vec::Vec;
 use bssl_avf_error::{ApiName, Error, Result};
@@ -31,6 +29,7 @@
     EC_KEY_set_public_key_affine_coordinates, EC_POINT_get_affine_coordinates,
     NID_X9_62_prime256v1, NID_secp384r1, BIGNUM, EC_GROUP, EC_KEY, EC_POINT,
 };
+use cbor_util::{get_label_value, get_label_value_as_bytes};
 use ciborium::Value;
 use core::ptr::{self, NonNull};
 use coset::{