Add extra otlp attrs for OpenTlemetry tracing

[penglongli]

Summary

ArgoCD now support OpenTlemetry with grpc by parameter otlp-address. But users cannot set extra attributes. We propose adding a param otlp-attrs to support it.

Because some users may have some requirements, such as: add token, carry cluster information, etc.

Motivation

Please give examples of your use case, e.g. when would you use this.

argocd-application-controller --otlp-address report-otlp.example.com --otlp-attrs "token:fake,cluster:test"

Proposal

With this proposal, need do:

• Add command line execution parameters to input otlp attributes, such as otlp-attrs
• Function trace.InitTracer() add otlpAttrs([]string) param support.