Make the `structlog` integration for Sentry logs

### Problem Statement

`structlog` logs can be sent to Sentry via the existing `LoggingIntegration`; however, this does not preserve the structuring of the logs (e.g. if the logs have custom attributes set, these are included in the log message). See [this example](https://github.com/getsentry/sentry-python/issues/4417#issuecomment-2910640972)

### Solution Brainstorm

Instead, create a dedicated `structlog` integration, which would add these logs to the log event as custom attributes.