add description for spring properties added in 2.6.0

[zeitlinger]

look at the changes in additional-spring-configuration-metadata.json

• config properties support for spring starter clients #11605
• Use config properties for spring starter (http server) #11667
• support otel.instrumentation.common.default-enabled in spring starter #11746

All instrumentations now support the same properties as the agent, so it makes sense to redirect or to extract pages that can be re-used: open-telemetry/opentelemetry.io#4758

We can also document the missing properties for the agent: open-telemetry/opentelemetry.io#4804 (done)

• otel.instrumentation.http.client.emit-experimental-telemetry
• otel.instrumentation.http.server.emit-experimental-telemetry
• otel.instrumentation.http.known-methods