Add numeric elapsed_seconds to metrics JSON

Resolves #2506

genMetrics.py stores stage runtimes as human-readable strings
(e.g., "0:04.26") which are hard to consume programmatically.
This adds numeric elapsed_seconds fields (in seconds as floats)
alongside the existing string fields so runtimes are directly
usable for analysis and plotting.

New fields added per stage:
  - <stage>__elapsed_seconds (float, seconds)
  - total_elapsed_seconds (float, seconds)

Existing fields (runtime__total, total_time) are unchanged.

Signed-off-by: Harsh Kumar Patwa <harshkumarpatwa@gmail.com>
Signed-off-by: Harsh Kumar <harshkumar3446@gmail.com>

Author: harsh-kumar-patwa

flow/util/genMetrics.py

@@ -315,6 +315,7 @@ def extract_metrics(
 
     failed = False
     total = timedelta()
+    elapsed_seconds = {}
     for key in metrics_dict:
         if key.endswith("__runtime__total"):
             # Big try block because Hour and microsecond is optional
@@ -341,10 +342,16 @@ def extract_metrics(
             )
             total += delta
 
+            stage = key.removesuffix("__runtime__total")
+            elapsed_seconds[stage + "__elapsed_seconds"] = delta.total_seconds()
+
     if failed:
         metrics_dict["total_time"] = "ERR"
     else:
         metrics_dict["total_time"] = str(total)
+        metrics_dict["total_elapsed_seconds"] = total.total_seconds()
+
+    metrics_dict.update(elapsed_seconds)
 
     metrics_dict = {
         key.replace(":", "__"): value for key, value in metrics_dict.items()