Rename histogram configuration bucketbounds to boundaries

[cijothomas]

Better aligned with spec term: https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/sdk.md#explicit-bucket-histogram-aggregation

[codecov]

Codecov Report

Merging #2638 (5d37528) into main (1be29c8) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #2638      +/-   ##
==========================================
+ Coverage   80.95%   80.96%   +0.01%     
==========================================
  Files         243      243              
  Lines        8547     8547              
==========================================
+ Hits         6919     6920       +1     
+ Misses       1628     1627       -1     

Impacted Files	Coverage Δ
...ry/Metrics/ExplicitBucketHistogramConfiguration.cs	42.85% <100.00%> (ø)
...elemetry/Metrics/MeterProviderBuilderExtensions.cs	81.81% <100.00%> (ø)
src/OpenTelemetry/Metrics/MeterProviderSdk.cs	93.12% <100.00%> (ø)
...ter.ZPages/Implementation/ZPagesActivityTracker.cs	97.14% <0.00%> (-2.86%)	⬇️
src/OpenTelemetry/Metrics/AggregatorStore.cs	86.80% <0.00%> (+0.69%)	⬆️
...Telemetry/Internal/SelfDiagnosticsEventListener.cs	97.65% <0.00%> (+0.78%)	⬆️