CHEF-2414 Deprecate azure connections from train

[sathish-progress]

Note: inspec-azure will continue to work. Using inspec exec -t azure:// will continue to work.

Warns the users that long unused Azure connections from train would be deprecated.

Description

As part of removing the long unused Azure SDKs from train, this change is the first part where we let know the users about deprecating this Azure Connection.
While target platform azure meaning -t azure would still continue to work.
Things that will be deprecated -

• msi authentication
• any azure SDK based connections including graph rbac, vault, storage. These resources are long supported in inspec-azure cloud resource packs through non-SDK means using latest Azure APIs and they will continue to exist.

Related Issue

second part: #745
https://chefio.atlassian.net/browse/CHEF-2414

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New content (non-breaking change)
• Breaking change (a content change which would break existing functionality or processes)

Checklist:

• I have read the CONTRIBUTING document.

[clintoncwolfe]

I'm going to ask that we do this without using ActiveSupport. We try to keep it out of train-core (and no, azure transport is not in train-core) but I think the only reason train has an active_support dependency was due to azure. I think active support dependencies need to be well-justified. Here we could get by with a warning.