1. Add manifest and CNAB replication tests;
2. Duplicate ORAS and sigularity tests from API test to nightly common
tests;
3. Optimize get dns code in CI;
4. Optimize E2E dockerfile;
5. Sample image size should be cover requirement for large size like 512M.
Signed-off-by: danfengliu <danfengl@vmware.com>
