[Feature]: Upgrade Cassandra backend to storage v2 API

[Manik2708]

Requirement

Child issue of #6458

• Implement ptrace.Traces <-> dbmodel converter
• Implement WriteTraces
• Implement GetTraces
• Implement FindTraces
• Implement FindTraceID
• Implement GetServices
• Implement GetOperations
• Fix dbmodel having no space to store scope and link attributes.

Problem

Cassandra currently uses this flow: ptrace.Traces <-> model.Trace <-> dbmodel.Span, the model.Trace layer needs to be removed to change the flow to ptrace.Traces <-> dbmodel.Span

Proposal

No response

Open questions

No response