1. Proposed title of this feature request?

Improve opentelemetry error message from invalid duplicate mountPath error to missing container in multi-sidecar deployments.

2. What is the nature and description of the request?

To clearly state when a container listed for instrumentation in the annotation instrumentation.opentelemetry.io/container-names is missing from the deployment's Pod spec section, instead of showing duplicate ** mountPath error:

Pod <pod_name> is invalid: spec.containers[0].volumeMounts[9].mountPath: Invalidvalue: "/otel-auto-instrumentation-java-app": must be unique. 

3. Why does the customer need this? (List the business requirements here)

The current error message is misleading i.e. it points to duplicate mountPath instead of a missing container, forcing users to spend significant time debugging the incorrect part of the YAML.

4. List any affected packages or components.

Red Hat build of OpenTelemetry Operator (Tested for v0.135.0)