Support filtering Issue Alerts by event attribute stacktrace.function

### Problem Statement

We would like to trigger issue alerts for issues crashing in specific functions. The issue alert filters support creating filters based on most of the event stack trace components, aside from the function.

stack.function is already supported in metric alerts.

### Solution Brainstorm

_No response_

### Product Area

Alerts

Start by locating the issue alert filter handling and compare it with the existing metric alert support for stack.function. The work is complete when issue alerts can filter on the stacktrace.function event attribute consistently with the other supported stack trace components.

Written by the indexing model from the issue text.