Embeddable URL for Dashboard widget or saved Discovery query

### Problem Statement

A user of ours would like to embed Sentry widgets and saved queries into other pages/tools they use. One example is having a Notion dashboard that tracks high-level health of their systems from multiple sources, and they would love to add Sentry visualizations there. Currently we don't have embeddable URLs for use cases like these.

### Solution Brainstorm

_No response_

### Product Area

Dashboards

┆Issue is synchronized with this [Jira Improvement](https://getsentry.atlassian.net/browse/FEEDBACK-1972) by [Unito](https://www.unito.io)