Unified Monitoring Agent enhancements for Canada Southeast (Toronto)

The following Unified Monitoring Agent changes have been implemented for Canada Southeast (Toronto):

• The realm domain is now obtained from the instance metadata service, rather than the SDK.
• Added support for resource principal to sign HTTP requests.
• The new nested JSON parser type has been added.
• Metrics related to the validity of the configuration downloaded by the agent are now emitted.
• Warning message issues have been fixed.