Support latest API

We currently don't support the latest API capabilities from Sentry. For example, we currently fetch issues via the [org API](https://github.com/grafana/sentry-datasource/blob/586e6ab0ec3e747fd322c4ea305cd7d7aab7b7e7/pkg/sentry/issues.go#L73) route ([docs](https://docs.sentry.io/api/organizations/)) but that doesn't seem officially supported anymore?