[Maps] Telemetry fixes & updates

[kindsun]

Tracking issue for Maps telemetry bug fixes and updates:

• Move telemetry out from under attributes nesting ([Maps] Remove extra layer of telemetry nesting under "attributes" #66137)

• Change telemetry name back to 'maps' ([Maps] Remove extra layer of telemetry nesting under "attributes" #66137, [Maps] New mappings: maps-telemetry -> maps #69816)

• Remove unused telemetry saved object ([Maps] Remove maps-telemetry saved object as it is no longer in use #69871)

• Add saved object placeholder. Not necessary for telemetry but required for formerly used saved objects. Requested by platform team ([Maps] Add maps telemetry saved object in with mappings disabled #69995)

• Fix telemetry undercounting issue, originally captured in [Maps][Telemetry] Maps telemetry undercounts map usage #51345 (PR: [Maps] Iterate over saved object & index patterns pages to collect telemetry results #73077)

• Update telemetry to capture EMS and custom layer usage. Related: [Telemetry] Collector Schema #64942, [telemetry] Fix Maps telemetry with dynamic fields #38394

[elasticmachine]

Pinging @elastic/kibana-gis (Team:Geo)