ref(crons): Update monitor incident title and subtitle (#102727)

Changes monitor incident issue title from "Monitor failure" to "Cron
failure" and updates the subtitle to include the specific failure reason
instead of the generic "Your monitor has reached its failure threshold"
message.

Fixes [NEW-552: Add Cron monitor failure reason to the event's
message](https://linear.app/getsentry/issue/NEW-552/add-cron-monitor-failure-reason-to-the-events-message)

Author: evanpurkhiser

src/sentry/monitors/logic/incident_occurrence.py

@@ -160,19 +160,21 @@ def send_incident_occurrence(
             owner_actor = None
             monitor_env.monitor.update(owner_user_id=None, owner_team_id=None)
 
+    failure_reason = get_failure_reason(previous_checkins)
+
     occurrence = IssueOccurrence(
         id=uuid.uuid4().hex,
         resource_id=None,
         project_id=monitor_env.monitor.project_id,
         event_id=uuid.uuid4().hex,
         fingerprint=[incident.grouphash],
         type=MonitorIncidentType,
-        issue_title=f"Monitor failure: {monitor_env.monitor.name}",
-        subtitle="Your monitor has reached its failure threshold.",
+        issue_title=f"Cron failure: {monitor_env.monitor.name}",
+        subtitle=f"Your monitor is failing: {failure_reason}.",
         evidence_display=[
             IssueEvidence(
                 name="Failure reason",
-                value=str(get_failure_reason(previous_checkins)),
+                value=str(failure_reason),
                 important=True,
             ),
             IssueEvidence(

tests/sentry/monitors/logic/test_incident_occurrence.py

@@ -106,8 +106,8 @@ def test_send_incident_occurrence(
             **{
                 "project_id": self.project.id,
                 "fingerprint": [self.incident.grouphash],
-                "issue_title": f"Monitor failure: {self.monitor.name}",
-                "subtitle": "Your monitor has reached its failure threshold.",
+                "issue_title": f"Cron failure: {self.monitor.name}",
+                "subtitle": "Your monitor is failing: 1 timeout and 1 error check-ins detected.",
                 "resource_id": None,
                 "evidence_data": {},
                 "evidence_display": [
@@ -191,8 +191,8 @@ def test_send_incident_occurrence_detector(
             **{
                 "project_id": self.project.id,
                 "fingerprint": [self.incident.grouphash],
-                "issue_title": f"Monitor failure: {self.monitor.name}",
-                "subtitle": "Your monitor has reached its failure threshold.",
+                "issue_title": f"Cron failure: {self.monitor.name}",
+                "subtitle": "Your monitor is failing: 1 timeout and 1 error check-ins detected.",
                 "resource_id": None,
                 "evidence_data": {"detector_id": detector.id},
                 "evidence_display": [