chore: refactor cibuildwheel.utils (#2252)

* chore: refactor cibuildwheel.utils

* rework build_frontend extra flags

* ci(fix): use tonistiigi/binfmt:qemu-v8.1.5 image for qemu

unit_test/oci_container_test.py

@@ -16,6 +16,7 @@ import pytest
 import tomli_w
 
 import cibuildwheel.oci_container
+from cibuildwheel.ci import CIProvider, detect_ci_provider
 from cibuildwheel.environment import EnvironmentAssignmentBash
 from cibuildwheel.errors import OCIEngineTooOldError
 from cibuildwheel.oci_container import (
@@ -24,7 +25,6 @@ from cibuildwheel.oci_container import (
     OCIPlatform,
     _check_engine_version,
 )
-from cibuildwheel.util import CIProvider, detect_ci_provider
 
 # Test utilities