Reduce allocations for invocations that have non-cancelable tokens

[AArnott]

This change avoids an allocation if the cancellationToken passed in by the caller is the default CancellationToken.None.

[codecov-io]

Codecov Report

Merging #353 into master will decrease coverage by 3.07%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #353      +/-   ##
==========================================
- Coverage   90.56%   87.48%   -3.08%     
==========================================
  Files          37       37              
  Lines        2438     2438              
  Branches        0      474     +474     
==========================================
- Hits         2208     2133      -75     
+ Misses        230      225       -5     
- Partials        0       80      +80

Impacted Files	Coverage Δ
src/StreamJsonRpc/JsonRpc.cs	91.52% <100%> (-1.77%)	⬇️
src/StreamJsonRpc/RequestId.cs	77.27% <0%> (-18.19%)	⬇️
src/StreamJsonRpc/StreamMessageHandler.cs	88.23% <0%> (-11.77%)	⬇️
src/StreamJsonRpc/Reflection/MethodSignature.cs	66.66% <0%> (-11.12%)	⬇️
src/StreamJsonRpc/RequestIdJsonConverter.cs	77.77% <0%> (-11.12%)	⬇️
...pc/Reflection/MessageFormatterDuplexPipeTracker.cs	86.84% <0%> (-7.9%)	⬇️
src/StreamJsonRpc/Reflection/TargetMethod.cs	89.39% <0%> (-7.58%)	⬇️
...nRpc/Reflection/MessageFormatterProgressTracker.cs	85.96% <0%> (-7.02%)	⬇️
src/StreamJsonRpc/JsonMessageFormatter.cs	86.92% <0%> (-6.21%)	⬇️
src/StreamJsonRpc/Protocol/JsonRpcError.cs	76.47% <0%> (-5.89%)	⬇️
... and 9 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 2e50b63...014bbf2. Read the comment docs.

[AArnott]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).