Update enterprise getting started guide with Day 2

This update includes dividing the enterprise getting started guide into two days with Day 1 for onboarding platform engineers and Day 2 for expanding capabilities. It helps the users to follow the flow more intuitively. It also includes the enabling process of write access to Git and cluster management via Cluster API. The move towards a day-by-day guide contributes to a more structured and digestible learning process.

Signed-off-by: Eneko Fernandez <eneko@weave.works>