[Request]: Rewrite o11y intros to highlight OTel

[theletterf]

Description

Some of the introductory / get started docs for obs under Solutions don't feature OTel at all or don't talk of it as the first and preferred option for ingest.

This PR explores how OTel could be presented in those pages.

Resources

https://docs.google.com/document/d/1IxAx2Ww_Ap15rFcGPimklKFvlF42ix407vzxcDv--n8/edit?tab=t.0

Which documentation set does this change impact?

Stateful and Serverless

Feature differences

Identical in stateful and serverless.

What release is this request related to?

9.0

Collaboration model

The product team

Point of contact.

Main contact: @theletterf

Stakeholders: @akhileshpok @mlunadia @AlexanderWert