Capture body for HTTP requests + incoming messages

### Classic agent link
- https://www.elastic.co/guide/en/apm/agent/java/current/config-core.html#config-capture-body

### What it does
For transactions that are HTTP requests, the Java agent can optionally capture the request body (e.g. POST variables). For transactions that are initiated by receiving a message from a message broker, the agent can capture the textual message body.

### Implementation difficulty, location, and dynamism
- Already implemented
- https://opentelemetry.io/docs/zero-code/java/agent/configuration/#capturing-servlet-request-parameters
- https://opentelemetry.io/docs/zero-code/java/agent/configuration/#capturing-consumer-message-receive-telemetry-in-messaging-instrumentations
- Not dynamic

@akhileshpok please feedback on whether this really needs to be supported as a dynamic capability