Observability: Update OpenTelemetry doc

[Izabela Kulakowska]

Is your feature request related to a problem? Please describe.

In some sections, the term OpenTelemetry Agent seems to refer directly to the OpenTelemetry java agent jar.
In case of Java, the java agent offers the automatic instrumentation but for other languages it’s not necessarily the “agent” that provides that.
Besides that, in the official OpenTelemetry documentation, the OpenTelemetry Agent is defined as the Collector deployment type
and is not related to the automatic instrumentation that is available for some languages.
The nomenclature inconsistence between OpenTelemetry docs and information in the playbook can be confusing for readers.

The section integration-options-with-azure-monitor describes only Java use case as it compares two Java agents jar files available. But it's not mentioned explicitly that the section is relevant only for Java.

Describe the solution you'd like

• Update the OpenTelemetry doc to be more generic and language agnostic.
• Provide links to the OpenTelemetry documentation for more information/details on the OpenTelemetry concepts.
• Make the usage of OpenTelemetry Agent term consistent with the OpenTelemetry documentation