fix(provider/azure): Add Application Name Validator for Azure

[neil-yechenwei]

Currently spinnaker doesn't validate application name for azure.
So add an application name validator for azure.

[spinnakerbot]

The following commits need their title changed:

• f6159dc: add application name validation for azure

• 6e012ca: update regex

Please format your commit title into the form:

<type>(<scope>): <subject>, e.g. fix(kubernetes): address NPE in status check

This allows us to easily generate changelogs & determine semantic version numbers when cutting releases. You can read more about commit conventions here.

[mybayern1974]

@sbwsg , @lwander , @duftler , a kindly ping to review this PR. The purpose of this PR is, without this fix, the user is likely to create an invalid application name that will be used in the later Azure deploy stage, in which things will break w/o friendly error notifications. So the PR is to prevent that at the very beginning.

[duftler]

I think SpinnakerBot is pointing out that the commit message needs its format updated, not that the PR description needs its format updated.

[maggieneterval]

@neil-yechenwei this looks good to go, would you mind resolving the conflicts when you get a chance so we can merge? Thanks!