more tests and restrict NESTED_XX to snapshot

Author: ChrisHegarty

x-pack/plugin/esql/src/internalClusterTest/java/org/elasticsearch/xpack/esql/action/ForkIT.java

@@ -262,6 +262,32 @@ public void testSortAndLimitOnlyInSecondSubQuery() {
         }
     }
 
+    public void testLimitOnlyInFirstSubQuery() {
+        var query = """
+            FROM test
+            | FORK
+               ( LIMIT 100 )
+               ( WHERE content:"fox" )
+            | SORT _fork, id
+            | KEEP _fork, id, content
+            """;
+        try (var resp = run(query)) {
+            assertColumnNames(resp.columns(), List.of("_fork", "id", "content"));
+            assertColumnTypes(resp.columns(), List.of("keyword", "integer", "text"));
+            Iterable<Iterable<Object>> expectedValues = List.of(
+                List.of("fork1", 1, "This is a brown fox"),
+                List.of("fork1", 2, "This is a brown dog"),
+                List.of("fork1", 3, "This dog is really brown"),
+                List.of("fork1", 4, "The dog is brown but this document is very very long"),
+                List.of("fork1", 5, "There is also a white cat"),
+                List.of("fork1", 6, "The quick brown fox jumps over the lazy dog"),
+                List.of("fork2", 1, "This is a brown fox"),
+                List.of("fork2", 6, "The quick brown fox jumps over the lazy dog")
+            );
+            assertValues(resp.values(), expectedValues);
+        }
+    }
+
     public void testLimitOnlyInSecondSubQuery() {
         var query = """
             FROM test

x-pack/plugin/esql/src/main/antlr/EsqlBaseLexer.g4

@@ -223,8 +223,8 @@ LEFT_BRACES : '{';
 RIGHT_BRACES : '}';
 
 NESTED_WHERE : WHERE -> type(WHERE);
-NESTED_SORT : SORT -> type(SORT);
-NESTED_LIMIT : LIMIT -> type(LIMIT);
+NESTED_SORT : {this.isDevVersion()}? SORT -> type(SORT);
+NESTED_LIMIT : {this.isDevVersion()}? LIMIT -> type(LIMIT);
 
 NAMED_OR_POSITIONAL_PARAM
     : PARAM (LETTER | UNDERSCORE) UNQUOTED_ID_BODY*