workload/schemachanger: version gate INSPECT command

Previously, the schema changer workload was incorrectly executing the
INSPECT command in a mixed version setting. This patch adds version gate
to add expected errors if INSPECT is not supported at the current
version.

Fixes: #156704

Release note: None

Author: fqazi

pkg/workload/schemachange/operation_generator.go

@@ -3508,6 +3508,17 @@ func (og *operationGenerator) inspect(ctx context.Context, tx pgx.Tx) (*opStmt,
 	sb.WriteString(" WITH OPTIONS DETACHED")
 	stmt.sql = sb.String()
 
+	// If INSPECT is not supported yet, so we expect a syntax error or feature
+	// not supported.
+	isInspectUnsupported, err := isClusterVersionLessThan(ctx, tx, clusterversion.V25_4.Version())
+	if err != nil {
+		return nil, err
+	}
+	if isInspectUnsupported {
+		stmt.expectedExecErrors.add(pgcode.FeatureNotSupported)
+		stmt.expectedExecErrors.add(pgcode.Syntax)
+	}
+
 	return stmt, nil
 }