group dataset files (elastic#118739) (elastic#119045)

*.csv files used for creating data and *.csv-spec used to define test scenarios are blending in the resource directory.
This change moves all *.csv files to data/*.csv so that it is easier to distinguish between data and specs.
This allows to have a quicker overview of existing data when starting a new spec.

x-pack/plugin/esql/qa/testFixtures/src/main/java/org/elasticsearch/xpack/esql/CsvTestsDataLoader.java

@@ -362,7 +362,7 @@ private static void load(RestClient client, TestsDataset dataset, Logger logger,
         if (mapping == null) {
             throw new IllegalArgumentException("Cannot find resource " + mappingName);
         }
-        final String dataName = "/" + dataset.dataFileName;
+        final String dataName = "/data/" + dataset.dataFileName;
         URL data = CsvTestsDataLoader.class.getResource(dataName);
         if (data == null) {
             throw new IllegalArgumentException("Cannot find resource " + dataName);

x-pack/plugin/esql/src/test/java/org/elasticsearch/xpack/esql/CsvTests.java

@@ -423,7 +423,7 @@ private static CsvTestsDataLoader.TestsDataset testsDataset(LogicalPlan parsed)
     }
 
     private static TestPhysicalOperationProviders testOperationProviders(CsvTestsDataLoader.TestsDataset dataset) throws Exception {
-        var testData = loadPageFromCsv(CsvTests.class.getResource("/" + dataset.dataFileName()), dataset.typeMapping());
+        var testData = loadPageFromCsv(CsvTests.class.getResource("/data/" + dataset.dataFileName()), dataset.typeMapping());
         return new TestPhysicalOperationProviders(testData.v1(), testData.v2());
     }