text: Title: Provide an option to pass DB_SSLMODE for postgres
  Body: /kind bug
  
  **What steps did you take and what happened:**
  [A clear and concise description of what the bug is.]
  We are trying to connect Katib to Azure flexible postgres database, but the connection fails due to disabled ssl mode https://github.com/kubeflow/katib/blob/f4c8861c810cc3088beebe9578932151850eafd1/pkg/db/v1beta1/postgres/postgres.go#L53
  
  **What did you expect to happen:**
  There should be a dedicated variable which can be used to pass the required value. In our case, Ssl Mode=Require;
  
  **Anything else you would like to add:**
  [Miscellaneous information that will assist in solving the issue.]
  
  **Environment:**
  Nonprod/prod
  
  - Katib version (check the Katib controller image version): katib-controller:v0.14.0
  - Kubernetes version: (`kubectl version`): v1.26.3
  - OS (`uname -a`): Ubuntu
  
  ---
  
  <!-- Don't delete this message to encourage users to support your issue! -->
  
  Impacted by this bug? Give it a 👍 We prioritize the issues with the most 👍
  