[Log Parsing Pipelines] Filters referencing resources.* fields don't work

[raj-k-singh]

When trying pipelines with filters like resources.service_name = some-service, if the actual logs have nil resources, collector logs end up being spammed with logs like

"2023-11-02T18:27:59.697Z warn router/router.go:119 Running expression returned an error {"kind": "processor", "name": "logstransform/pipeline_test", "pipeline": "logs", "operator_id": "router_signoz", "operator_type": "router", "error": "cannot fetch service_name from <nil> (1:11)\n | resources.service_name == \"some-service\"\n | ..........^"}"

Also the larger issue here is that even though the Signoz log model has a resources field, the field does not seem to be available on plog data structure provided to logtransform processor by the collector