az: migrate all to using private.json

[gjwgit]

The new method for handling the Azure Services key is through the CONFIGURE command, using the private: entry in MLHUB.yaml.

Migrate each of the az models to using this approach:

• [x] azcv
• [x] azface
• [x] azlang
• [x] azluis
• [x] azspeech
• [x] aztext
• [x] aztranslate

[gjwgit]

Merge azluis into azlang.

[JingjingShii]

I remove canned.pkl because I don't think we allow users to run demo in azlang without private information.