Enable training for pybindings (pytorch#12144)

### Summary
Let's support the (experimental) training modules out of the box for our
wheels.

### Test plan

```
$ ./install_executorch.sh
$ python3

>>> import torch
>>> from executorch.extension.training.pybindings import _training_lib
```

cc @JacobSzwejbka

Author: jathu

tools/cmake/preset/pybind.cmake

@@ -20,6 +20,8 @@ set_overridable_option(EXECUTORCH_BUILD_KERNELS_CUSTOM_AOT ON)
 set_overridable_option(EXECUTORCH_BUILD_EXTENSION_FLAT_TENSOR ON)
 set_overridable_option(EXECUTORCH_BUILD_EXTENSION_DATA_LOADER ON)
 set_overridable_option(EXECUTORCH_BUILD_KERNELS_OPTIMIZED ON)
+set_overridable_option(EXECUTORCH_BUILD_EXTENSION_MODULE ON)
+set_overridable_option(EXECUTORCH_BUILD_EXTENSION_TRAINING ON)
 
 
 if(CMAKE_SYSTEM_NAME STREQUAL "Darwin")