Add Agent's Computer Name to metric

[cbat98]

This PR augments the azure_devops_agentpool_agent_info metric by adding the agent's computer name as a label. This can be useful for grouping agents by the server that they're running on for use in Grafana dashboards. Whilst I personally prefer the term "Server Name", "Computer Name" was chosen as it more closely matches the capability that is exposed by the Agent Software (Agent.ComputerName).

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[sonarqubecloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[cbat98]

Are you able to take a look at this please @mblaschke ? Thank you :D