Adds account level and workspace level operations for ngwaf rules using json file inputs

[anthony-gomez-fastly]

Change summary

Add support for NGWAF rule manipulation. create and update are handled by allowing the user to proved a valid json that can be unmarshalled to the matching structure for the given rule level.

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[rcaril]

One potential small area for improvement, otherwise looks good.

Thanks for putting a considerable effort into this PR!