[HUD] Add average PR landing time metric (#6956)

Adds a hud metric to track the average pull request landing time for the
PyTorch repository. Specifically, it tracks the time from the initial
merge attempt to the first successful merge (only considers merged PRs).


Query perf:
```
+------+----------+-----------+
| Test | Avg Time |  Avg Mem  |
+------+----------+-----------+
|  0   |   1215   | 264834466 |
|  1   |   1268   | 272445089 |
|  2   |   1076   | 267499089 |
+------+----------+-----------+
```

### Testing:

Locally. See the preview.

Author: izaitsevfb

torchci/clickhouse_queries/pr_landing_time_avg/params.json

@@ -0,0 +1,20 @@
+{
+  "params": {
+    "startTime": "DateTime64(3)",
+    "stopTime": "DateTime64(3)"
+  },
+  "tests": [
+    {
+      "startTime": "2024-12-20T00:00:00.000",
+      "stopTime": "2024-12-27T00:00:00.000"
+    },
+    {
+      "startTime": "2024-12-01T00:00:00.000",
+      "stopTime": "2024-12-31T23:59:59.999"
+    },
+    {
+      "startTime": "2024-11-01T00:00:00.000",
+      "stopTime": "2024-11-30T23:59:59.999"
+    }
+  ]
+}

torchci/clickhouse_queries/pr_landing_time_avg/query.sql

@@ -0,0 +1,51 @@
+-- Query to calculate average PR landing time for recent period
+-- Landing time = time from first "Merge started" comment to when PR was merged
+WITH
+-- Find the first "Merge started" comment for each PR
+merge_started AS (
+    SELECT
+        toUInt32(extractGroups(issue_url, 'issues/([0-9]+)')[1]) AS pr_number,
+        MIN(created_at) AS first_merge_attempt
+    FROM default.issue_comment
+    WHERE
+        dynamoKey LIKE 'pytorch/pytorch%'
+        AND user.login = 'pytorchmergebot'
+        AND body LIKE '%Merge started%'
+        AND created_at >= {startTime: DateTime64(3)}
+        AND created_at <= {stopTime: DateTime64(3)}
+    GROUP BY pr_number
+),
+
+-- Find when PRs were merged (closed with Merged label)
+merged_prs AS (
+    SELECT
+        number AS pr_number,
+        parseDateTimeBestEffort(closed_at) AS merge_time
+    FROM default.pull_request
+    WHERE
+        dynamoKey LIKE 'pytorch/pytorch%'
+        AND state = 'closed'
+        AND arrayExists(x -> x.'name' = 'Merged', labels)
+        AND closed_at != ''
+        AND parseDateTimeBestEffort(closed_at) >= {startTime: DateTime64(3)}
+        AND parseDateTimeBestEffort(closed_at) <= {stopTime: DateTime64(3)}
+),
+
+-- Calculate landing time for each PR
+pr_landing_times AS (
+    SELECT
+        ms.pr_number,
+        DATE_DIFF('minute', ms.first_merge_attempt, mp.merge_time)
+        / 60.0 AS landing_time_hours
+    FROM merge_started ms
+    INNER JOIN merged_prs mp ON ms.pr_number = mp.pr_number
+    WHERE
+        -- Ensure merge happened after merge attempt
+        mp.merge_time > ms.first_merge_attempt
+        AND landing_time_hours < 168  -- Exclude outliers > 1 week
+        AND landing_time_hours > 0   -- Exclude negative times
+)
+
+-- Return average landing time in hours
+SELECT ROUND(AVG(landing_time_hours), 2) AS avg_hours
+FROM pr_landing_times

torchci/pages/metrics.tsx

@@ -752,6 +752,28 @@ export default function Page() {
           </Stack>
         </Grid2>
 
+        <Grid2
+          container
+          size={{ xs: 6, md: 3, lg: 2 }}
+          justifyContent={"stretch"}
+        >
+          <Stack
+            justifyContent={"space-between"}
+            flexGrow={1}
+            flexWrap="wrap"
+            spacing={1}
+          >
+            <ScalarPanel
+              title={"PR landing time (avg)"}
+              queryName={"pr_landing_time_avg"}
+              metricName={"avg_hours"}
+              valueRenderer={(value) => value.toFixed(1) + "h"}
+              queryParams={timeParams}
+              badThreshold={(value) => value > 24} // 24 hours
+            />
+          </Stack>
+        </Grid2>
+
         <Grid2
           container
           size={{ xs: 6, md: 3, lg: 2 }}