Get Sentry Comments on Suspect Un-merged Pull Requests

### Problem Statement

The [Get Sentry Comments on Suspect Pull Requests](https://docs.sentry.io/product/integrations/source-code-mgmt/github/#get-sentry-comments-on-suspect-pull-requests) works on **merged** PRs; described in the docs, “If a recently merged pull request is suspected of causing an issue …“). Currently, the PR needs to be merged into the main branch because we are mapping the merge commit sha of the suspect commit to the PR. code [here](https://github.com/getsentry/sentry/blob/5d37dc1c7d9c4dc2e6238e85db987dea5b42e70b/src/sentry/tasks/commit_context.py#L81-L95)

This is limiting for developers who want to see errors **before** their associated PRs are merged. If the sentry-io bot comment were also added to an un-merged PR, then that would accommodate this developer workflow:
1. PR is deployed in a dev env
2. If there are issues there, then the bot will comment in the PR
3. This way, devs can fix it before releasing it prod

### Solution Brainstorm

_No response_

### Product Area

Issues

┆Issue is synchronized with this [Jira Improvement](https://getsentry.atlassian.net/browse/FEEDBACK-2038) by [Unito](https://www.unito.io)