Add canary toggle for Spinnaker application

[KeisukeYamashita]

WHAT

API to configure canary on/off for Spinnaker applications.

WHY

In the Spinnaker application level, we can configure either we enable canary or not.

[silvez-dh]

hello. Looking for a TF provider w/ this canary toggle option. Any chance to implement this any soon?

Thanks!