Metric instrumentation for Redis client

[cijothomas]

Similar to: https://github.com/open-telemetry/opentelemetry-dotnet/blob/main/src/OpenTelemetry.Instrumentation.AspNetCore/Implementation/HttpInMetricsListener.cs

[cijothomas]

spec incoming: https://github.com/open-telemetry/opentelemetry-specification/pull/2070/files

[tiagodaraujo]

I opened the PR #1982 to resolve this issue, I don't know if it was the best process. I added 3 new metrics with the same tracing attributes that follow the semantic convention.

Can anyone help me to understand the next steps or even what steps I skipped?