Switching from using legacyInstanceId to the Jenkins controller URL for the jenkinsResourceTag value, similar to the ec2-plugin. This could be a good way to handle duplicate legacyInstanceIds. It seems like this change could benefit multiple people.

This came from an issue where the Cleanup task was deprovisioning VMs after exactly 2 hours, interrupting any on-going builds. This is because the cleanLeakedResouces() method looks for candidate nodes to removed based on legacyInstanceId.

Fixes #634

With this PR:

• New Tags will be constructed using Jenkins URL <jenkinsURL>|<timestamp>
• Cleanup tasks will look for this new format, and also old format <id>/<timestamp>

Testing done

• Added unit tests for testing new format.
• No evil Jenkins on mvn hpi:run.
• Tested CleanupTask on old format: After building the plugin, I configured a Cloud, provisioned a node with a job, updated its tag in Azure to the 'id/ts' format (it correctly assigned the new "url|ts" format), and waited for the CleanupTask to remove it. The task successfully deleted the node.

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