Remove oteltest dependency from otelmux

[MrAlias]

Replace the use of the oteltest package with the sdk/trace/tracetest package for the otelmux instrumentation. Do this in its own test module to not impose a dependency on the default SDK to the instrumentation user.

This uses a pre-release version of the sdk/trace/tracetest to prepare for the next release of otel-go.

Part of open-telemetry/opentelemetry-go#2121

[codecov]

Codecov Report

Merging #897 (2339b3a) into main (05ba496) will decrease coverage by 0.2%.
The diff coverage is n/a.

@@           Coverage Diff           @@
##            main    #897     +/-   ##
=======================================
- Coverage   75.6%   75.4%   -0.3%     
=======================================
  Files         69      69             
  Lines       4458    4458             
=======================================
- Hits        3374    3363     -11     
- Misses       942     952     +10     
- Partials     142     143      +1     

Impacted Files	Coverage Δ
...mentation/github.com/gorilla/mux/otelmux/config.go	60.0% <0.0%> (-40.0%)	⬇️
...trumentation/github.com/gorilla/mux/otelmux/mux.go	81.4% <0.0%> (-8.7%)	⬇️

[pellared]

nice refactoring 😉

PS. Do we want to play with sth like https://github.com/ory/go-acc to more accurate code coverage results?

More: https://www.ory.sh/golang-go-code-coverage-accurate/

[MrAlias]

nice refactoring

PS. Do we want to play with sth like https://github.com/ory/go-acc to more accurate code coverage results?

More: https://www.ory.sh/golang-go-code-coverage-accurate/

Yes! I was looking for something exactly like this. I think we should try to incorporate this.