Nexus Operations request side metrics

[S15]

What changed?

New Metrics:

Counters

Metric	Description
nexus_request_error_count	Nexus requests that result in an error

New Labels:

For nexus_requests, nexus_request_error_count and nexus_latency. Most of these were already set on nexus_requests and nexus_latency

Label	Notes
namespace
nexus_endpoint
nexus_service	Controlled by Dynamic config
nexus_operation	Controlled by Dynamic config
nexus_caller
nexus_caller_type	Currently always "namespace"

How did you test it?

• built
• run locally and tested manually
• covered by existing tests
• added new unit test(s)
• added new functional test(s)

[S15]

Notes:
Waiting to hear back from @kepe-temporal on if we need to change the names of nexus_requests and nexus_latency.

Test failures are shared with feature/nexus-standalone branch.

[S15]

Not sure if there's a better way to do this. callerInfo.CallerType seems to be something else (which is maybe a hint that using callerInfo at all is wrong here?).

[bergundy]

Not reviewing this yet since we have all of the metrics in different forms already. Let's see what @kepe-temporal comes back with.

[kepe-temporal]

We can use the old metrics and rename them, but we can't split metrics across multiple tables on ingest depending on the value of a label.