[Logs Essentials] Create a Observability Serverless subscription tier page

[mdbirnstiehl]

Create a page for the different subscription tiers under Observability in the solutions docs. This page should:

• - Explain why to choose one over the other.
• - Provide a high-level comparison between the tiers.
• - Show users how to upgrade, and make it clear that they cannot go back to Logs Essentials once upgraded.
• - Link to pricing.
• - Provide data ingestion recommendations (MoTel for Logs Essentials)

reference doc