Fixing ActivitySource from DiagnosticSource

[eddynaka]

Fixes #1522

Changes

Please provide a brief description of the changes here.

For significant contributions please make sure you have completed the following items:

• CHANGELOG.md updated for non-trivial changes
• Design discussion issue #
• Changes in public API reviewed

[codecov]

Codecov Report

Merging #1515 (2bfd714) into master (d1c174d) will increase coverage by 0.06%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #1515      +/-   ##
==========================================
+ Coverage   81.34%   81.40%   +0.06%     
==========================================
  Files         233      233              
  Lines        6336     6358      +22     
==========================================
+ Hits         5154     5176      +22     
  Misses       1182     1182              

Impacted Files	Coverage Δ
...trumentation.SqlClient/SqlClientInstrumentation.cs	100.00% <ø> (ø)
...umentation.AspNet/Implementation/HttpInListener.cs	89.10% <100.00%> (+0.44%)	⬆️
...tation.AspNetCore/Implementation/HttpInListener.cs	86.56% <100.00%> (+0.41%)	⬆️
...ent/Implementation/GrpcClientDiagnosticListener.cs	87.75% <100.00%> (+1.08%)	⬆️
...tp/Implementation/HttpHandlerDiagnosticListener.cs	77.50% <100.00%> (+1.18%)	⬆️
src/OpenTelemetry/Trace/ActivitySourceAdapter.cs	97.05% <100.00%> (+0.28%)	⬆️

[eddynaka]

Running benchmark, I could not see any difference:
BEFORE

Method	Mean	Error	StdDev	Gen 0	Gen 1	Gen 2	Allocated
InstrumentedAspNetCoreGetPage	229.5 us	4.52 us	9.33 us	1.4648	-	-	2.21 KB

AFTER

Method	Mean	Error	StdDev	Gen 0	Gen 1	Gen 2	Allocated
InstrumentedAspNetCoreGetPage	226.8 us	4.18 us	3.91 us	1.4648	-	-	2.21 KB

[cijothomas]

Confirmed that this fixed the OTLPExporter issue :)

[cijothomas]

LGTM