fix: Add timeout settings and retry logic to MySQL connector

Configuration improvements:
- Set read_timeout=300 (5 minutes) to handle long queries
- Set write_timeout=300 (5 minutes) for writes
- Set max_allowed_packet=64MB to handle larger data transfers

Retry logic:
- Added retry mechanism with max 3 retries on fetch failure
- Auto-reconnect on connection loss before retry
- Better error messages showing retry attempts

This fixes the 'connection is lost' error that occurs during
long-running migrations by:
1. Giving MySQL queries more time to complete
2. Allowing larger packet sizes for bulk data
3. Automatically recovering from connection drops

Fixes: 'Connection is lost' error during full migration

config.py

@@ -156,13 +156,13 @@ _rawdatacor_config = {
     "mysql_table": "RAWDATACOR",
     "postgres_table": "rawdatacor",
     "primary_key": "id",
-    "partition_key": "event_date",
+    "partition_key": "event_timestamp",
 }
 _elabdatadisp_config = {
     "mysql_table": "ELABDATADISP",
     "postgres_table": "elabdatadisp",
     "primary_key": "idElabData",
-    "partition_key": "event_date",
+    "partition_key": "event_timestamp",
 }
 
 TABLE_CONFIGS = {