Make the service name configurable for project monitors

[paulb-elastic]

It is currently possible to set the APM service name (which corresponds to service.name) for Synthetic monitors when configuring them via the Synthetics UI:

However it is not possible to set this for project monitors.

The implementation will need to make changes in the Synthetic monitor definition as well as change in the Kibana API to support the new configuration.

The add monitor and update monitor APIs won’t need to be updated as they already include service.name, however the get monitor endpoint does not currently return service.name.

ACs:

• It is possible to define the service.name for project monitors
• This will be available for all monitor types
  • Browser
  • HTTP
  • TCP
  • ICMP
• Update the get monitor API endpoint to return service.name
  • Update the documentation