Stop validating View-provided stream Name against instrument name syntax

[cijothomas]

Per the OpenTelemetry specification clarification in open-telemetry/opentelemetry-specification#5094, the View-provided metric stream Name is NOT subject to the instrument name syntax and the SDK MUST NOT validate it against that syntax.

Removes name-syntax validation from MetricStreamConfiguration.Name setter, the AddView(instrumentName, name) overload, and the runtime check in MetricReaderExt (which now only validates names that originate from the instrument itself, not View-renamed names). Also removes the now-unused internal MeterProviderBuilderSdk.IsValidViewName. Direct instrument creation via Meter continues to enforce the syntax.

Spec PR: open-telemetry/opentelemetry-specification#5094

Update (2026-05-19): Spec PR open-telemetry/opentelemetry-specification#5094 has been merged.

[codecov]

Codecov Report

❌ Patch coverage is 75.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 89.92%. Comparing base (a7b3346) to head (a3e5d2a).
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
...rc/OpenTelemetry/Metrics/Reader/MetricReaderExt.cs	66.66%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7300      +/-   ##
==========================================
+ Coverage   89.87%   89.92%   +0.05%     
==========================================
  Files         276      276              
  Lines       14007    14001       -6     
==========================================
+ Hits        12589    12591       +2     
+ Misses       1418     1410       -8     

Flag	Coverage Δ
unittests-Project-Experimental	89.82% <75.00%> (-0.02%)	⬇️
unittests-Project-Stable	89.83% <75.00%> (+0.03%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
.../Metrics/Builder/MeterProviderBuilderExtensions.cs	98.52% <ø> (-0.03%)	⬇️
...lemetry/Metrics/Builder/MeterProviderBuilderSdk.cs	100.00% <ø> (ø)
...elemetry/Metrics/View/MetricStreamConfiguration.cs	100.00% <100.00%> (ø)
...rc/OpenTelemetry/Metrics/Reader/MetricReaderExt.cs	92.06% <66.66%> (+0.06%)	⬆️

... and 3 files with indirect coverage changes

[cijothomas]

@martincostello could you re-review and merge if all okay?