SplunkHecExporter: Add support for LogFormat.name field

[breedx-splk]

The Splunk HEC Exporter supports logs, but conversion of pdata.LogRecord into the splunk.Event does not pass along the name field. Right now, it appears that LogRecord.name is just dropped on the floor.

This field is optional in the spec, but if a user provides one it's probably needed/wanted and should be represented in the HEC data export.

There isn't a corresponding name field in the HEC Event type, so I see two possibilities:

• overload the splunk.sourceTypeLabel field (sounds complicated and have to handle conflicts in a sane way)
• cook up a well known attribute and add it to the HEC fields. I'll suggest otlp.log.name but am not married to it.