Define Infrastructure department strategy

Why is this change being made?

Inspired by a recent e-team drive to encourage contributions to the company strategy, proposing an Infrastructure Department strategy.

Since I (author of this MR) don't know what to contribute to the company strategy that is already not said, I thought it would be good to see how this will look on the department level.

In order to start on a strategy, I had to ensure that the mission and vision are up to date. The department strategy is laid out in a way that supports the company strategy but translated and expanded for Infrastructure specific environment:

1. Product Maturity and customer centricity I believe translate to performance, security and reliability in Infrastructure department
2. Open Core strength translates to generating external contributions
3. Team growth is also important in the department.

As everything is draft at GitLab, my suggestions are just that and I am open to hearing other views.

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