Keep methods with struct name and switch them to default (#6879)

* Keep methods with struct name and switch them to default

This PR can help fix the following two issues:
1): A set of simplified API (without struct name) was added in
https://github.com/google/flatbuffers/pull/6336. It causes name
conflict when merging all generated python file into a single one
(the primary usage senario in Google).
2): Flatbuffers 2.0 generates absolute import path, which may cause
name space conflicts. See more details in
https://github.com/google/flatbuffers/issues/5840.

The solution for both is to generate the merged Python code, similar
C++. The merged code will not contain the simplied API, but only the
method with struct name. For issue (1), it will mimic the exactly
usage pattern for Google internal. For issue (2), users can generate
the merged flatbuffer code, without worrying about the imports.

The above idea will be implemented in the following steps:
Step 1 (this PR): revert changes in https://github.com/google/flatbuffers/pull/6336
that set the simplified API as default. Remove statements that the
original API will be deprecated, and reset the original API as default.
Step 2 (the following PR): create a flag to generate the merged code.
The Simplified API will be removed from the merged code, otherwise it
will cause name conflict.

* Update the generated sample code

* Update the generated example code

* Reverst the changes of GetRootAs

* Update examples from grpc/example/generate.sh

tests/MyGame/Example/Stat.py

@@ -49,26 +49,21 @@ class Stat(object):
             return self._tab.Get(flatbuffers.number_types.Uint16Flags, o + self._tab.Pos)
         return 0
 
-def Start(builder): builder.StartObject(3)
-def StatStart(builder):
-    """This method is deprecated. Please switch to Start."""
-    return Start(builder)
-def AddId(builder, id): builder.PrependUOffsetTRelativeSlot(0, flatbuffers.number_types.UOffsetTFlags.py_type(id), 0)
-def StatAddId(builder, id):
-    """This method is deprecated. Please switch to AddId."""
-    return AddId(builder, id)
-def AddVal(builder, val): builder.PrependInt64Slot(1, val, 0)
-def StatAddVal(builder, val):
-    """This method is deprecated. Please switch to AddVal."""
-    return AddVal(builder, val)
-def AddCount(builder, count): builder.PrependUint16Slot(2, count, 0)
-def StatAddCount(builder, count):
-    """This method is deprecated. Please switch to AddCount."""
-    return AddCount(builder, count)
-def End(builder): return builder.EndObject()
-def StatEnd(builder):
-    """This method is deprecated. Please switch to End."""
-    return End(builder)
+def StatStart(builder): builder.StartObject(3)
+def Start(builder):
+    return StatStart(builder)
+def StatAddId(builder, id): builder.PrependUOffsetTRelativeSlot(0, flatbuffers.number_types.UOffsetTFlags.py_type(id), 0)
+def AddId(builder, id):
+    return StatAddId(builder, id)
+def StatAddVal(builder, val): builder.PrependInt64Slot(1, val, 0)
+def AddVal(builder, val):
+    return StatAddVal(builder, val)
+def StatAddCount(builder, count): builder.PrependUint16Slot(2, count, 0)
+def AddCount(builder, count):
+    return StatAddCount(builder, count)
+def StatEnd(builder): return builder.EndObject()
+def End(builder):
+    return StatEnd(builder)
 
 class StatT(object):
 
@@ -102,10 +97,10 @@ class StatT(object):
     def Pack(self, builder):
         if self.id is not None:
             id = builder.CreateString(self.id)
-        Start(builder)
+        StatStart(builder)
         if self.id is not None:
-            AddId(builder, id)
-        AddVal(builder, self.val)
-        AddCount(builder, self.count)
-        stat = End(builder)
+            StatAddId(builder, id)
+        StatAddVal(builder, self.val)
+        StatAddCount(builder, self.count)
+        stat = StatEnd(builder)
         return stat