Add OTLP/gRPC output driver

[andborja]

Summary

Adds a new otlp output driver that exports received Windows events to an OpenTelemetry (OTLP) endpoint over gRPC. Each event is mapped to an OpenTelemetry log record — the event content becomes the log body, and subscription/client information is attached as attributes.

Details

Event mapping: The event content is set as the log body. Windows event Level and TimeCreated are best-effort parsed from the raw event XML to populate the record's severity and timestamp; when absent or unparseable, severity falls back to INFO and the timestamp falls back to openwec's receive time.

Attributes:

• subscription.name
• subscription.uuid
• client
• client.address
• node (when available)

Configuration (OtlpConfiguration):

• endpoint — OTLP/gRPC endpoint (required)
• timeout — optional export timeout in seconds (1–300)
• compression — optional, gzip or zstd

Delivery semantics

Export runs inline in write() on the server's Tokio runtime, so failures propagate back to openwec and the batch is retried.

Testing

Added unit tests covering:

• Driver construction with valid config and gzip/zstd compression
• Level → OpenTelemetry Severity mapping and fallback for missing/unknown/non-numeric levels
• TimeCreated extraction (single/double quotes) and None on missing/invalid timestamps

[andborja]

@vruello, @WilliamBruneau, hopefully you can review this PR is the project is active