Refactors BoolQueryBuilder and Parser. Splits the parse(QueryParseCon…

…text ctx) method into a parsing

and a query building part, adding NamedWriteable implementation for serialization and hashCode(),
equals() for testing.

This change also adds tests using fixed set of leaf queries (Terms, Ids, MatchAll) as nested Queries in test query setup.
Also QueryParseContext is adapted to return QueryBuilder instances for inner filter parses instead of
previously returning Query instances, keeping old methods in place but deprecating them.

Relates to elastic#10217
Closes elastic#11427

core/src/main/java/org/elasticsearch/common/io/stream/StreamInput.java

@@ -509,6 +509,20 @@ public <C> C readNamedWriteable() throws IOException {
         return namedWriteable.readFrom(this);
     }
 
+    /**
+     * Reads a list of {@link NamedWriteable} from the current stream, by first reading its size and then
+     * reading the individual objects using {@link #readNamedWriteable()}.
+     */
+    public <C> List<C> readNamedWritableList() throws IOException {
+        List<C> list = new ArrayList<>();
+        int size = readInt();
+        for (int i = 0; i < size; i++) {
+            C obj = readNamedWriteable();
+            list.add(obj);
+        }
+        return list;
+    }
+
     public static StreamInput wrap(BytesReference reference) {
         if (reference.hasArray() == false) {
             reference = reference.toBytesArray();

core/src/main/java/org/elasticsearch/common/io/stream/StreamOutput.java

@@ -457,4 +457,15 @@ public void writeNamedWriteable(NamedWriteable namedWriteable) throws IOExceptio
         writeString(namedWriteable.getName());
         namedWriteable.writeTo(this);
     }
+
+    /**
+     * Writes a list of {@link NamedWriteable} to the current stream, by first writing its size and then iterating over the objects
+     * in the list
+     */
+    public void writeNamedWritableList(List<? extends NamedWriteable> list) throws IOException {
+        writeInt(list.size());
+        for (NamedWriteable obj : list) {
+            writeNamedWriteable(obj);
+        }
+    }
 }