Add Entity Store V2 support for performance tests

[gurevichdmitry]

Summary

Add Entity Store V2 support to performance tests.

Changes

• V2 / --noTransforms flow

  • Use --noTransforms for the Entity Store V2 (ESQL) flow

  • Enable and install V2 via doc-gen

  • Split upload logic into V1 and V2 paths

    • V2 writes to .entities.v2.latest*
    • No transforms or engines are used

  • Add helpers in kibana_api

  • Add constant for the V2 install URL

• Perf data updates

  • Add user.entity.id
  • Add event metadata (event.kind, event.category, event.type) for UEBA / postAggFilter
  • Add user.email as a string field
  • Extend UserFields with optional user.entity and event

• Docs

  • Update README and CLI docs to document --noTransforms and related behavior.