Update APM docs to reflect data streams

[bmorelli25]

Summary

• Update CCS documentation to reflect the data streams indexing pattern
• More coming...

More information

Experimental support for data streams will be added in 7.12. In 8.0, data streams will be required. Data streams will write to pre-specified, non-editable indices (logs-apm*, metrics-apm*, traces-apm*). More info: elastic/kibana#88329.

This comment elastic/kibana#87501 (comment) explains the new indexing strategy well:

errors -> logs-apm*
transactions -> traces-apm*
spans -> traces-apm*
metrics -> metrics-apm*

The new defaults for the events should therefore look like this:

transactionIndices: schema.string({ defaultValue: 'apm-*,traces-apm*' }), 
spanIndices: schema.string({ defaultValue: 'apm-*,traces-apm*' }), 
errorIndices: schema.string({ defaultValue: 'apm-*,logs-apm*' }), 
metricsIndices: schema.string({ defaultValue: 'apm-*,metrics-apm*' })

Other issues

• [Closed] Implement the new indexing strategy Implement the new indexing strategy apm-server#4378
• Kibana [APM] Add experimental support for Data Streams kibana#89650

[bmorelli25]

Moving to at least 7.13 as we're not updating any APM Server docs outside of the APM integration heading at this time.

• Fleet user guide PR: Add data stream docs to Fleet user guide #429, docs
• APM integration PR: docs: APM integration apm-server#4928, docs

[bmorelli25]

Already completed in 7.16.