Review and add tests for Nexus operation log and metrics labels.

[pdoerner]

Is your feature request related to a problem? Please describe.
Review the labels that are currently set on the metrics handler and logger returned from temporalnexus.GetMetricsHandler and temporalnexus.GetLogger. At the time of writing it is Nexus service, Nexus operation, and task queue.

Describe the solution you'd like
Any other useful labels should be added and tests should be updated to ensure they are being set appropriately.

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
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