Store new minidumps in issues

### Problem Statement

Curently when enabling "Store minidumps as attachment" Sentry saves the minidumps until the limit is reached and stops taking new ones. In this setup, the stored minidumps represent old events intead of the most recent events.

### Solution Brainstorm

Add the option to replace old minidumps with new ones in issues.

The current workarounds are: manually delete stored minidumps, or set limit to "unlimited".

### Product Area

Issues

Start by locating the implementation of the “Store minidumps as attachment” option and its storage-limit handling. Trace how stored minidumps are selected and replaced, then identify existing tests for this behavior. Done means new minidumps are retained while older stored minidumps are removed when the limit is reached.

Written by the indexing model from the issue text.