Adds an Attribute assertion to metric data test

[MadVikingGod]

This is an attempt to solve the immediate problem of #3435.

It creates a new Assert function that will check if the attributes on ALL DataPoints contain the Attributes provided.

[codecov]

Codecov Report

Attention: Patch coverage is 95.04132% with 6 lines in your changes missing coverage. Please review.

Project coverage is 78.0%. Comparing base (d7b3115) to head (6774d23).
Report is 1824 commits behind head on main.

Files with missing lines	Patch %	Lines
sdk/metric/metricdata/metricdatatest/assertion.go	89.1%	4 Missing ⚠️
...dk/metric/metricdata/metricdatatest/comparisons.go	97.6%	2 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #3487     +/-   ##
=======================================
+ Coverage   77.9%   78.0%   +0.1%     
=======================================
  Files        165     165             
  Lines      11634   11755    +121     
=======================================
+ Hits        9066    9179    +113     
- Misses      2372    2380      +8     
  Partials     196     196             

Files with missing lines	Coverage Δ
...dk/metric/metricdata/metricdatatest/comparisons.go	97.5% <97.6%> (+<0.1%)	⬆️
sdk/metric/metricdata/metricdatatest/assertion.go	80.6% <89.1%> (+5.2%)	⬆️

... and 1 file with indirect coverage changes

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