Trigger notification when alert configuration is changed

### Problem Statement

In our case, often an entire team has access to an alert. This means that person A might've created an alert but anyone from the team can modify it. Now whenever someone modifies the alert, person A is confused because they can't find out who changed their alert.

If person B modifies the alert threshold, there should be a way for person A to figure out what the previous config was. For example, say person B modified an alert's threshold temporarily but they forgot to change it back, now person A is trying to find out what their original alert config was.

### Solution Brainstorm

There could be 2 approaches for solving this.

1. Keep history of modifications

Similar to how Jira keeps a track of all changes on a ticket, Sentry can keep a history of the changes done to an alert. This would help figure out who changed the alert thresholds and when.

2. Provide a feature to trigger a Slack notification every time someone changes an alert's settings

The notification should include the person's email and which alert settings they modified.