Plumb error info to X-ray

[bmoffatt]

Issue #, if available:

None

Description of changes:

This change fixes a divergence in behavior between the go1.x runtime, and the provided.XYZ runtime family. In go1.x, the github.com/aws/aws-lambda-go/messages/InvokeResponse_Error struct is wrapped in a certain way and then presented to the AWS X-Ray services in Lambda's default trace documents. In the Lambda Runtime API, this structure is passed as the Lambda-Runtime-Function-Xray-Error-Cause header.

Lambda's Java Runtime Interface Client is one public reference of this behavior. https://github.com/aws/aws-lambda-java-libs/blob/3d8dfb66f3a852bf69618bd5f66222692f1f5a49/aws-lambda-java-runtime-interface-client/src/main/java/com/amazonaws/services/lambda/runtime/api/client/AWSLambda.java#L264

---

When X-Ray is enabled for a function, this populates the "Exceptions" tab when viewing a trace.

For reference, here's what the tab renders for a go1.x function.

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[codecov-commenter]

Codecov Report

Attention: 4 lines in your changes are missing coverage. Please review.

Comparison is base (3a93ed1) 72.95% compared to head (7ba157c) 73.30%.

Files	Patch %	Lines
lambda/invoke_loop.go	85.71%	2 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #544      +/-   ##
==========================================
+ Coverage   72.95%   73.30%   +0.34%     
==========================================
  Files          26       26              
  Lines        1457     1487      +30     
==========================================
+ Hits         1063     1090      +27     
- Misses        322      324       +2     
- Partials       72       73       +1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.