Factor generic logic out of security/index.jsx

These pieces of logic will likely be useful for helpers in other places of the code, so it would be useful to extract them as separate helper functions, but that's totally non-mandatory for now, and can be done in another PR.

_Originally posted by @tyxla in https://github.com/Automattic/jetpack/pull/14098/files_

Read security/index.jsx and the discussion or diff from pull request 14098 to identify which logic is generic and which parts are specific to the security screen. Done means the reusable logic is separated without changing current behavior; the issue does not name a test file or verification command.

Written by the indexing model from the issue text.