[DOCS-7210] Service owners guide

[aliciascott]

What does this PR do? What is the motivation?

New Services Owners guide.

• Purpose of this document is to learn things about what it means to implement Datadog as a Service owner
• It will address several different audiences , mainly the persona of a service owner - someone who needs to understand the best practices of setting up Datadog to avoid pit-falls down the road

Merge instructions

• [ ] Please merge after reviewing

Additional notes