[Epic] Rich Slack Notifications

[ceorourke]

Product Spec

Tech Spec

Convert notifications to use block kit

- [ ] https://github.com/getsentry/sentry/issues/61456
- [ ] https://github.com/getsentry/sentry/issues/61457
- [ ] https://github.com/getsentry/sentry/issues/61459
- [ ] https://github.com/getsentry/sentry/issues/61460
- [ ] https://github.com/getsentry/sentry/issues/61461
- [ ] https://github.com/getsentry/sentry/issues/61463
- [ ] https://github.com/getsentry/sentry/issues/61465
- [ ] https://github.com/getsentry/sentry/issues/61464
- [ ] https://github.com/getsentry/sentry/issues/61468

Message formatting updates

- [ ] https://github.com/getsentry/sentry/issues/62899
- [ ] https://github.com/getsentry/sentry/issues/62901
- [ ] https://github.com/getsentry/sentry/issues/62902
- [ ] https://github.com/getsentry/sentry/issues/62904
- [ ] https://github.com/getsentry/sentry/issues/62905
- [ ] https://github.com/getsentry/sentry/issues/63147
- [ ] https://github.com/getsentry/sentry/issues/63152
- [ ] https://github.com/getsentry/sentry/issues/63642
- [ ] https://github.com/getsentry/sentry/issues/64116

[getsantry[bot]]

Routing to @getsentry/product-owners-alerts for triage ⏲️

[mfn]

Moved to https://github.com/getsentry/sentry/issues/64984