Add serverless mode support to Profiler

[chynesNR]

This adds the ability to add an instrumentation point to the Profiler via an environment variable, AWS_LAMBDA_FUNCTION_NAME, in the format assembly::class::method. If the variable is not in the correct format it will log a Warning but continue running. It does not attempt to verify that the method exists.

The environment variable can be added at any point during the startup sequence and the Profiler will pick it up (as long as the method hasn't been invoked yet)..

When the named method is invoked it will call the wrapper NewRelic.Providers.Wrapper.AwsLambda.HandlerMethod in the managed Agent.

Unit tests are included.

This also removes the hard-coded method name in the instrumentation.xml that was used in the POC branch.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 28 lines in your changes are missing coverage. Please review.

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Additional details and impacted files

@@                    Coverage Diff                    @@
##             feature/lambda-support    #2285   +/-   ##
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  Coverage                          ?   72.80%           
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  Files                             ?      444           
  Lines                             ?    27749           
  Branches                          ?     3021           
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  Hits                              ?    20202           
  Misses                            ?     6769           
  Partials                          ?      778           

Files	Coverage Δ
...c/Agent/NewRelic/Profiler/Common/AssemblyVersion.h	0.00% <0.00%> (ø)
...rc/Agent/NewRelic/Profiler/Configuration/Strings.h	0.00% <0.00%> (ø)
...t/NewRelic/Profiler/MethodRewriter/Instrumentors.h	0.00% <0.00%> (ø)
...filer/Configuration/InstrumentationConfiguration.h	0.00% <0.00%> (ø)

[tippmar-nr]

Looks good!