Fix SigNoz cache span filtering

[ejsmith]

Summary

• Drop successful Redis spans regardless of the exporting service name.
• Match both db.system and the newer db.system.name semantic-convention attribute.
• Preserve Redis spans whose status is STATUS_CODE_ERROR and retain the existing Message: EntityChanged filter.

Root cause

The cache-span filter was scoped to two fixed service.name values. A deployment renamed a service, so its successful Redis spans stopped matching the filter and were exported to SigNoz.

Validation

• git diff --check
• Rendered signoz/k8s-infra chart 0.16.0 with helm template and confirmed filter/drop_cache_spans is present in the node-agent traces pipeline after chart-injected processors and before batch.

Breaking changes

None.

[github-actions]

Package	Line Rate	Branch Rate	Complexity	Health
Exceptionless.Insulation	37%	35%	286	❌
Exceptionless.Core	75%	67%	10184	✔
Exceptionless.Web	85%	69%	7903	✔
Exceptionless.AppHost	38%	41%	147	❌
Summary	78% (25156 / 32154)	67% (11809 / 17554)	18520	✔