Additional improvements to time series data stream docs

[marciw]

Not yet prioritized

specific:

• link to EDOT quickstart from TSDS quickstart + TSDS OTLP page (Add custom metrics quickstart guide for EDOT #4219 (comment))
• OTLP: edit more thoroughly
• Reindex: explain op_type (add something like "ensures the operation is idempotent")
• Reindex: update to "better path" mentioned here
• Querying DS page title: change to # Querying downsampled data in {{es}} (see comment)
• Double-check deployment options and recommended approaches, and separate from true best practices

general:

• More glue (and consistency) with general data streams docs
• Other cross-linking opportunities
• More ES|QL TS command coverage (examples etc.)
• Any additional advanced operations