…as values for these types. It also fixes the issue when summary has no quantiles, allow it to produce a summary with nil snapshots

…receiver-starttime

# Conflicts:
#	receiver/prometheusreceiver/internal/metricsbuilder.go
#	receiver/prometheusreceiver/internal/metricsbuilder_test.go
#	receiver/prometheusreceiver/internal/ocastore_test.go
#	receiver/prometheusreceiver/internal/transaction.go
#	receiver/prometheusreceiver/metrics_receiver_test.go

…receiver-starttime

…iver-starttime

# Conflicts:
#	receiver/prometheusreceiver/internal/metrics_adjuster.go