Remove comparable constraint on Readers.

[MadVikingGod]

This refactors a how a pipeline is configured from a map[Reader][]views to a slice of structs{ Reader, []views, pipeline }.

This change will remove any requirement on comparability but will enable users to use the same Reader twice, which is an error.

This would address #3085

[codecov]

Codecov Report

Merging #3202 (24a8e01) into main (b6d4335) will increase coverage by 0.0%.
The diff coverage is 100.0%.

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #3202   +/-   ##
=====================================
  Coverage   77.4%   77.4%           
=====================================
  Files        158     158           
  Lines      11084   11088    +4     
=====================================
+ Hits        8583    8589    +6     
+ Misses      2306    2304    -2     
  Partials     195     195           

Impacted Files	Coverage Δ
sdk/metric/config.go	100.0% <100.0%> (ø)
sdk/metric/pipeline.go	97.3% <100.0%> (+<0.1%)	⬆️
sdk/metric/provider.go	100.0% <100.0%> (ø)
sdk/trace/batch_span_processor.go	81.9% <0.0%> (+0.8%)	⬆️

[MrAlias]

This looks like an good change. I don't think there needs to be a new registryEntry type introduced though. It can all be merged into a pipeline as is done in #3233.

[MadVikingGod]

I will close this, as the approach will probably differ after #3233.