Issue #1912316 by vijaycs85, sandipmkhairnar, YesCT: Create configuration schemas for dblog module.

core/modules/dblog/config/schema/dblog.schema.yml

+# Schema for the configuration files of the dblog module.
+
+dblog.settings:
+  type: mapping
+  label: 'Database logging settings'
+  mapping:
+    row_limit:
+      type: integer
+      label: 'Database log messages to keep'