Performance: HEC requests not batched, causing high load on Splunk

[tbdev77]

The current implementation sends one HTTP request to HEC per Event Hub message:

for (const event of eventHubMessages) {
    await splunk.sendToHEC(event, ...)  // One HTTP call per event
}

Under high volume, this can overwhelm Splunk Heavy Forwarders/HEC endpoints.

Proposed Fix

Batch all events from the Event Hub trigger into a single HEC payload before sending.
HEC supports concatenated JSON events in one request.

Impact

- Reduce HTTP overhead
- Improve throughput
- Reduce load on Splunk infrastructure