Refactor CA certificate handling

[fmoc]

Currently, custom CA certificates not trusted by default are stored within the account, but they need to be added to the global state to make requests in various network jobs work.

Instead of using the global state, we should rework our network access manager(s) to store custom the CA certificates and inject them on new requests (e.g., in createRequest).

Since we plan to introduce a custom network access manager for the core jobs as well, this is the perfect opportunity to reduce the amount of duplicate code and move common behavior into a common (abstract) base class.

[github-actions[bot]]

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