Allow customization of the SSLHelper initialization timeout

[yeikel]

Describe the feature

In Vertx 4.3.4, we changed how the SSLHelper is constructed and hardcoded it to 1 minute

This change is causing problems for an application that have a great amount of blocking initialization code

Ideally, this parameter should be customizable (system property should be fine) until a better long term solution can be archived. Not all blocking code is easily replaceable at this point for us as many of the components are legacy components that we don't own

Use cases

Applications that have a great amount of blocking code during initialization will have problems to create an instance of the SSLHelper within 1 minute

Contribution

If we agree that a System property is appropriate, I can give it a shot.