Summary:
Empty fields are allowed in CertManager. Removed checks for string length
Check whether edit zone passes empty string when fields are removed

Test Plan:
- Send empty fields for cert manager during create and edit
- Modify some fields among kind, name and group to see correct fields are updated

Reviewers: jmak, svarshney

Reviewed By: jmak

Subscribers: yugaware

Differential Revision: https://phorge.dev.yugabyte.com/D41917