Add the SampledFilter exemplar Reservoir implementation

[MrAlias]

This Reservoir implementation is used at the MeterProvider level to pre-filter measurements offered to a wrapped Reservoir.

Part of #559

This PR is split from #4455

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (08beb8b) 82.3% compared to head (79ffca9) 82.3%.

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #4851   +/-   ##
=====================================
  Coverage   82.3%   82.3%           
=====================================
  Files        227     228    +1     
  Lines      18563   18569    +6     
=====================================
+ Hits       15292   15300    +8     
+ Misses      2983    2981    -2     
  Partials     288     288           

Files	Coverage Δ
sdk/metric/internal/exemplar/filter.go	100.0% <100.0%> (ø)

... and 1 file with indirect coverage changes