Unified Monitoring Agent enhancements for UK Gov South (London) and UK Gov West (Newport)

The following Unified Monitoring Agent changes have been implemented for the UK Gov South (London) and UK Gov West (Newport) regions:

• 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.