Add benchmark on collection load time

[tellet-q]

• Add new column collection_load_time_ms to benchmark table
• Introduce BENCHMARK_STRATEGY variable to control the flow of the workflow (default | tenants | collection-load)
• Only push telemetry data into Postgres if BENCHMARK_STRATEGY is set to collection-load

Right now the dataset under test is random-768-100-tenants

[tellet-q]

I updated Grafana dashboard:

[tellet-q]

Example run: https://github.com/qdrant/vector-db-benchmark/actions/runs/10899422726

[tellet-q]

Let's have this benchmark in a separate repo.