feat(dbt): add pypi source and deps_dev distribution metadata source (#2602)

Author: ccerv1

warehouse/dbt/models/deps_dev_sources.yml

@@ -5,3 +5,6 @@ sources:
     tables:
       - name: dependencies
         identifier: Dependencies
+      - name: package_versions_latest
+        identifier: PackageVersionsLatest
+

warehouse/dbt/models/pypi_sources.yml

@@ -0,0 +1,9 @@
+sources:
+  - name: pypi
+    database: bigquery-public-data
+    schema: pypi
+    tables:
+      - name: distribution_metadata
+        identifier: distribution_metadata        
+      - name: file_downloads
+        identifier: file_downloads