Handle duplicate Aggregators and log instrument conflicts

[MrAlias]

When a Meter is asked to create an instrument that already exists...

• If it is the exact same instrument, it should return the same instance and update the already created Aggregators.
• If it is not the exact same, but does share a name, it should return a new instrument with new Aggregators but log the collision as a warning.

This PR updates the metric SDK to achieve these things. It does this with the following.

• Add the cache type described in Unify metric SDK caching #3245
• Add an instrumentCache that wraps two caches. One to cache instrument aggregations and ensure they are unique. The other to cache resolved view instrumentIDs so any conflicting creations are logged (something recommended by the spec).
• Maintain caches at a Meter level. This ensures that no duplicate instruments are issued per instrumentation scope. It also ensures that instrument conflicts are appropriately logged as such per instrumentation scope.
• Refactor the pipeline data storage. Instruments are de-duplicated prior to being passed to the pipeline, stop checking for duplicates when added to the pipeline.
  • This allows for the storage type to drop one level of maps.

Part of #3245
Fix #3240
Fix #3229

[codecov]

Codecov Report

Merging #3251 (b913d7a) into main (ffa94ca) will increase coverage by 0.1%.
The diff coverage is 93.6%.

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #3251     +/-   ##
=======================================
+ Coverage   77.5%   77.6%   +0.1%     
=======================================
  Files        160     161      +1     
  Lines      11203   11280     +77     
=======================================
+ Hits        8690    8763     +73     
- Misses      2313    2317      +4     
  Partials     200     200             

Impacted Files	Coverage Δ
sdk/metric/instrument.go	83.3% <ø> (ø)
sdk/metric/pipeline.go	93.9% <90.1%> (-1.0%)	⬇️
sdk/metric/cache.go	100.0% <100.0%> (ø)
sdk/metric/meter.go	100.0% <100.0%> (ø)

[MadVikingGod]

Only minor nits.