Capability checks for tests using dense_vector (elastic#129694)

Author: ioanatia

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

@@ -2371,6 +2371,7 @@ public void testImplicitCasting() {
     }
 
     public void testDenseVectorImplicitCasting() {
+        assumeTrue("dense_vector capability not available", EsqlCapabilities.Cap.DENSE_VECTOR_FIELD_TYPE.isEnabled());
         Analyzer analyzer = analyzer(loadMapping("mapping-dense_vector.json", "vectors"));
 
         var plan = analyze("""

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

@@ -1362,6 +1362,9 @@ public void testMultiMatchOptionsPushDown() {
     }
 
     public void testKnnOptionsPushDown() {
+        assumeTrue("dense_vector capability not available", EsqlCapabilities.Cap.DENSE_VECTOR_FIELD_TYPE.isEnabled());
+        assumeTrue("knn capability not available", EsqlCapabilities.Cap.KNN_FUNCTION.isEnabled());
+
         String query = """
             from test
             | where KNN(dense_vector, [0.1, 0.2, 0.3],