fix: Include an error type in provider error events

[kinyoklion]

Requirements

• I have added test coverage for new or changed functionality
• I have followed the repository's pull request submission guidelines
• I have validated my changes against all supported platform versions

Related issues

OFP requirement 5.1.5 (sdk-specs OFP-openfeature-provider-behavior): PROVIDER_ERROR events SHOULD populate the event details' error code.

Describe the solution you've provided

StatusProvider.EmitProviderEvent sets ProviderEventPayload.ErrorType = ErrorType.General for ProviderEventTypes.ProviderError events (emitted when the LaunchDarkly data source is Off). Added ProviderTests.ItIncludesAnErrorTypeInErrorEvents.

Describe alternatives you've considered

A more specific type (e.g. ProviderFatal for 401/403) was not used; OFP does not define a mapping, and the Python provider already uses GENERAL for the same transition.

Additional context

Validated locally with dotnet test on net8.0 (69 passed).

Link to Devin session: https://app.devin.ai/sessions/929f5530882d40bc95e55391e97536d5
Open in Devin Desktop: https://app.devin.ai/desktop/session/929f5530882d40bc95e55391e97536d5?variant=devin
Requested by: @kinyoklion

[devin-ai-integration]

I'll fix CI failures and address comments from users with write access. I'll skip comments containing "(aside)".

• Disable automatic comment, CI, and merge conflict monitoring