refactor: rename Batch to Partition across pipeline

Rename internal types and channels from Batch to Partition for consistency with the data model.

config.yaml

@@ -1,11 +1,13 @@
-max_parallel_workers: 2
+max_parallel_workers: 4
+source_db_type: sqlserver
+target_db_type: postgres
 
 defaults:
-  max_extractors: 4
-  max_loaders: 8
+  max_extractors: 2
+  max_loaders: 4
   queue_size: 8
-  chunk_size: 50000
-  chunks_per_batch: 10
+  chunk_size: 25000
+  chunks_per_batch: 8
   truncate_target: true
   truncate_method: TRUNCATE # TRUNCATE | DELETE
   retry:
@@ -21,19 +23,6 @@ jobs:
     target:
       schema: demo
       table: users
-    max_extractors: 2 # overrides default config
-    max_loaders: 4 # overrides default config
-    queue_size: 4 # overrides default config
-    chunk_size: 25000 # overrides default config
-    chunks_per_batch: 8 # overrides default config
-    truncate_target: false # overrides default config
-    truncate_method: DELETE # overrides default config
-    retry:
-      attempts: 5 # overrides default config
-    pre_sql:
-      - "SELECT 1"
-    post_sql:
-      - "SELECT 2"
 
   - name: analytics_events
     enabled: true