[Feature request]: Add per-worker thresholds for N+1 query detection

### Problem Statement

Currently, Sentry applies N+1 query detection thresholds globally at the project level. While you can adjust the overall threshold in Settings → Performance, there’s no way to tune detection sensitivity for specific background workers or tags. The customer would like to request more granular controls so that different workloads can have different N+1 time thresholds.

## Feedback from the customer

300ms is a very reasonable duration for queries that need to result in responses to users. But we rely on workers to offload long-running actions that might actually involve equally long-running DB-queries. These should still be monitored but allowed a longer duration.

### Solution Brainstorm

_No response_

### Product Area

Performance

Start by reviewing the existing project-level N+1 query detection threshold and the Performance settings area. Determine how background workers and tags are represented, then define how per-worker thresholds should be configured and applied. Done means different workloads can use distinct N+1 time thresholds while remaining monitored.

Written by the indexing model from the issue text.