Downgrade FetchSize log messages from WARN to DEBUG (#1237)

## Summary
- Downgrade `setFetchSize()` and `getFetchSize()` log messages from
`WARN` to `DEBUG` in both `DatabricksStatement` and
`DatabricksResultSet`
- SQLWarnings are still added per JDBC spec so callers can discover the
unsupported feature

## Root Cause
BI tools like Metabase call `setFetchSize()`/`getFetchSize()` on every
query as part of standard JDBC usage. Each call logged a WARN-level
message, flooding logs with thousands of warnings for expected, harmless
behavior.

## Test plan
- [x] `DatabricksStatementTest` — 83 tests pass
- [x] `DatabricksResultSetTest` — 53 tests pass

Fixes #1208

🤖 Generated with [Claude Code](https://claude.com/claude-code)

NO_CHANGELOG=true

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: gopalldb

src/main/java/com/databricks/jdbc/api/impl/DatabricksResultSet.java

@@ -760,15 +760,19 @@ public void setFetchSize(int rows) throws SQLException {
     Hence, we don't support it.*/
     LOGGER.debug("public void setFetchSize(int rows = {})", rows);
     checkIfClosed();
-    addWarningAndLog("As FetchSize is not supported in the Databricks JDBC, ignoring it");
+    String warningString = "As FetchSize is not supported in the Databricks JDBC, ignoring it";
+    LOGGER.debug(warningString);
+    warnings = WarningUtil.addWarning(warnings, warningString);
   }
 
   @Override
   public int getFetchSize() throws SQLException {
     LOGGER.debug("public int getFetchSize()");
     checkIfClosed();
-    addWarningAndLog(
-        "As FetchSize is not supported in the Databricks JDBC, we don't set it in the first place");
+    String warningString =
+        "As FetchSize is not supported in the Databricks JDBC, we don't set it in the first place";
+    LOGGER.debug(warningString);
+    warnings = WarningUtil.addWarning(warnings, warningString);
     return 0;
   }
 

src/main/java/com/databricks/jdbc/api/impl/DatabricksStatement.java

@@ -350,7 +350,7 @@ public void setFetchSize(int rows) {
     LOGGER.debug(String.format("public void setFetchSize(int rows = {%s})", rows));
     String warningString = "As FetchSize is not supported in the Databricks JDBC, ignoring it";
 
-    LOGGER.warn(warningString);
+    LOGGER.debug(warningString);
     warnings = WarningUtil.addWarning(warnings, warningString);
   }
 
@@ -360,7 +360,7 @@ public int getFetchSize() {
     String warningString =
         "As FetchSize is not supported in the Databricks JDBC, we don't set it in the first place";
 
-    LOGGER.warn(warningString);
+    LOGGER.debug(warningString);
     warnings = WarningUtil.addWarning(warnings, warningString);
     return 0;
   }