Feature Request: API Endpoint for originally accepted Events with environment data

### Problem Statement

Currently, there is no direct API endpoint that provides originally accepted events along with their environment values. While the Stats API shows events that were accepted within a given time window and Discover/API reflects [what is currently in storage](https://github.com/getsentry/sentry/issues/80885#issuecomment-2489124344), there is a gap when it comes to retrieving event counts based on their originally accepted state while also filtering or grouping by environment.

### Solution Brainstorm

_No response_

### Product Area

APIs

Start by reviewing the Stats API and Discover/API behavior described in the issue, including the linked discussion about current storage. Define the endpoint's accepted-event counting, environment filtering, and grouping requirements before implementation. Done means the API can retrieve counts from the originally accepted state with environment filters or grouping.

Written by the indexing model from the issue text.