Updated WandbLogger to make uploading model checkpoints optional

[manangoel99]

This PR adds a minor patch to the WandbLogger integration to make saving model checkpoints to the W&B dashboard optional. To save checkpoints to the dashboard, the users just need to update the yaml file like so

wandb:
    project: my_project
    entity: my_team
    log_checkpoint: true

Logging checkpoints is turned off by default.

[paddle-bot-old[bot]]

Thanks for your contribution!

[manangoel99]

I was wondering if I could get some feedback on this PR whenever possible

[manangoel99]

Hi @LDOUBLEV @WenmuZhou I was wondering if it would be possible to get a review on this PR

[manangoel99]

@WenmuZhou I've made the requested change