change gateway mode from statefulset to deployment

[pierreedbrg]

based on this issue open-telemetry/opentelemetry-operator#186 and the fix at open-telemetry/opentelemetry-operator#302, it adds support for tolerations in otelcol CRD, This helps in running Otel collectors on tainted nodes for both deployments and daemon sets.

the actual configuration

gateway.tolerations has no effect