Use span flags to derive service entry spans (referred to as top level operations)

[srikanthccv]

The change open-telemetry/opentelemetry-proto#484 adds a bit flag that helps to decide if a span is an entry-level span of the service. Today we run mat view to deduce them by joining the signoz_index_v2 table with itself. We should move away from the mat view to the bit flag.

1. This requires that SDKs send data and Users update the SDK version. But it's important that SDK implement this.
2. Add a column to signoz_index_v2 and relevant tables that indicate whether a span is a service entry span.
3. Update the APM metrics to use this column instead
4. Enabled APM metrics to dashboard/alerts

[srikanthccv]

Now available in sdks java, dotnet, go, and soon python