Add EDOT data streams documentation and clarify exporter/storage behavior

[alexandra5000]

Summary

This PR adds a new documentation page titled “EDOT data streams”, addressing recurring user questions.

The new page explains:

• Why EDOT configurations sometimes include two exporters (otel and ecs)

• Which data streams are populated by EDOT in OTel-native and ECS/APM-compatible modes

• Differences in data streams between mOTLP and local EDOT deployments

• Why some fields appear duplicated

• Which storage engines are used (TSDB, LogsDB)

Closes #3501

Generative AI disclosure

Did you use a generative AI (GenAI) tool to assist in creating this contribution?

• Yes
• No

If you answered "Yes" to the previous question, please specify the tool(s) and model(s) used (e.g., Google Gemini, OpenAI ChatGPT-4, etc.).

Tool(s) and model(s) used:
Claude 4.5 Sonnet via Cursor

[github-actions]

Vale Linting Results

Summary: 19 suggestions found

💡 Suggestions (19)

File	Line	Rule	Message
docs/reference/compatibility/data-streams.md	23	Elastic.WordChoice	Consider using 'refer to (if it's a document), view (if it's a UI element)' instead of 'see', unless the term is in the UI.
docs/reference/compatibility/data-streams.md	45	Elastic.Acronyms	'ECS' has no definition.
docs/reference/compatibility/data-streams.md	49	Elastic.WordChoice	Consider using 'refer to (if it's a document), view (if it's a UI element)' instead of 'See', unless the term is in the UI.
docs/reference/compatibility/data-streams.md	53	Elastic.Acronyms	'ECS' has no definition.
docs/reference/compatibility/data-streams.md	125	Elastic.Acronyms	'ECS' has no definition.
docs/reference/compatibility/data-streams.md	125	Elastic.Acronyms	'ECS' has no definition.
docs/reference/compatibility/data-streams.md	153	Elastic.Acronyms	'ECS' has no definition.
docs/reference/compatibility/data-streams.md	153	Elastic.Acronyms	'ECS' has no definition.
docs/reference/data-streams.md	3	Elastic.Acronyms	'ECS' has no definition.
docs/reference/data-streams.md	19	Elastic.Acronyms	'ECS' has no definition.
docs/reference/data-streams.md	23	Elastic.WordChoice	Consider using 'refer to (if it's a document), view (if it's a UI element)' instead of 'see', unless the term is in the UI.
docs/reference/data-streams.md	27	Elastic.WordChoice	Consider using 'can, might' instead of 'may', unless the term is in the UI.
docs/reference/data-streams.md	30	Elastic.Acronyms	'ECS' has no definition.
docs/reference/data-streams.md	45	Elastic.Acronyms	'TSDB' has no definition.
docs/reference/data-streams.md	51	Elastic.Acronyms	'ECS' has no definition.
docs/reference/data-streams.md	70	Elastic.Acronyms	'ECS' has no definition.
docs/reference/data-streams.md	76	Elastic.WordChoice	Consider using 'can, might' instead of 'may', unless the term is in the UI.
docs/reference/data-streams.md	85	Elastic.Acronyms	'ECS' has no definition.
docs/reference/data-streams.md	99	Elastic.Acronyms	'TSDB' has no definition.

[github-actions]

🔍 Preview links for changed docs

• docs/reference/data-streams.md
• docs/reference/compatibility/data-streams.md