Consolidate field names constants in a single place

[crespocarlos]

Summary

There are AFAIK 3 different locations where constants for field names are defined

• https://github.com/elastic/kibana/blob/main/x-pack/plugins/observability_solution/observability_shared/common/field_names/elasticsearch.ts
• https://github.com/elastic/kibana/blob/main/packages/kbn-apm-types/src/es_fields/apm.ts
• https://github.com/elastic/kibana/blob/main/x-pack/plugins/observability_solution/infra/common/constants.ts

observability_shared could be the centralized location for defining these constants, allowing other observability solution plugins to reuse them.

[elasticmachine]

Pinging @elastic/obs-ux-infra_services-team (Team:obs-ux-infra_services)

[ArchitGajjar]

Hi @crespocarlos - Can I work on this issue ? this would be my first contribution to this project ? Thank you!