CLOUDP-87735: global secret configuration

[antonlisovenko]

This PR allows the user to override the global API key Secret by passing the global-api-secret-name argument to the container. If the flag not provided - the name defaults to the <deployment_name>-api-key

As this cannot be tested by integration tests I've tested this manually: changed the deployment spec to the following:

- args:
          - --atlas-domain=https://cloud-qa.mongodb.com
          - --health-probe-bind-address=:8081
          - --metrics-bind-address=127.0.0.1:8080
          - --leader-elect
          - --global-api-secret-name=the-global-key
          command:
          - /manager

and ensured, that the new Secret was used by the Operator instead of the default one