[Lens as code] Remove Reference Line from ES|QL layers

[nickofthyme]

Summary

Changes:

• Removes reference line in schemas for ES|QL Lens charts.
• Keeps existing logic to handle ES|QL reference lines in place.
• Infills types to support ES|QL ref lines in logic.
• Add @depracated to infilled types until support is added in the UI.
• Renames referenceLines type to reference_lines.

Checklist

• Unit or functional tests were updated or added to match the most common scenarios
• The PR description includes the appropriate Release Notes section, and the correct release_note:* label is applied per the guidelines
• Review the backport guidelines and apply applicable backport:* labels.

[walterra]

Code LGTM.

[elasticmachine]

💛 Build succeeded, but was flaky

• Buildkite Build
• Commit: acb6f4d

Failed CI Steps

• FTR Configs #61
• Scout: [ security / entity_store ] plugin

Test Failures

• [job] [logs] Scout: [ security / entity_store ] plugin / local-stateful-classic - ESQL query translation - host: ESQL from doc with host.name + host.domain returns expected document(s)
• [job] [logs] FTR Configs #61 / serverless search UI Rule details Edit rule with deleted connector should show and update deleted connectors when there are existing connectors of the same type

Metrics [docs]

Async chunks

Total size of all lazy-loaded chunks that will be downloaded as the user navigates the app

id	before	after	diff
agentBuilder	815.9KB	815.9KB	+46.0B
cases	2.0MB	2.0MB	+39.0B
dashboard	866.8KB	866.8KB	+46.0B
dashboardAgent	138.0KB	138.0KB	+46.0B
discover	1.6MB	1.6MB	+39.0B
infra	1.3MB	1.3MB	+46.0B
lens	2.0MB	2.0MB	+35.0B
observability	2.0MB	2.0MB	+39.0B
observabilityAIAssistantApp	332.0KB	332.0KB	+46.0B
unifiedDocViewer	424.8KB	424.9KB	+46.0B
total			+428.0B