[FEATURE] Introduce a feature flag to disable Security screens

[derek-ho]

Is your feature request related to a problem? Today, the security screens are shown if you have valid permissions (defined via opensearch.yml). However, there may be situations where people don't want the security dashboards plugin to show up at all (for example if they only want to modify security settings with the admin cert, or APIs, etc.). We should introduce a feature flag that disables the security plugin screens from showing up regardless of the permissions of the user. What solution would you like? Feature flag in opensearch_dashboards.yml that disables the screens no matter what. What alternatives have you considered? None Do you have any additional context? None