Fix compilation errors in GCP M4 tests

- Remove unused corev1 import from appframework_gcs_test.go
- Remove unused corev1 import from manager_appframework_test.go
- Remove all remaining MC code from 3 test functions in manager_appframework_test.go
- Fixes undefined: corev1 errors at lines 843, 1440, 1576

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: gabrielm-splunk