bindings: python: examples: close chip objects where needed

bindings: python: examples: close chip objects where needed

Unlike the C++ bindings: we can't expect the python runtime to call
the Chip object's destructor when all references are dropped. We need
to close each chip explicitly. Either call the close() method directly
or use controlled execution in all examples.

Signed-off-by: Bartosz Golaszewski <bartekgola@gmail.com>