Issue

#6937

Description

middleware-recursion-detection performs a request header check that is case-sensitive.
This PR changes this check to be case-insensitive.

Testing

Added unit tests.

Also:

1. Have LambdaX and LambdaY, LambdaX invokes LambdaY via Lambda invoke from @aws-sdk/client-lambda, add permissions to LambdaX to use invoke.
2. Modified middleware-recursion-detection in node_modules of the LambdaX to make the trace header check case-insensitive
3. Enable Lambda service traces in both LambdaX and LambdaY
4. Enable Application Signals in LambdaX both LambdaX and LambdaY
5. Invoke LambdaX function.
6. Observed that middleware-recursion-detection will correctly not inject the trace header when calling lambdaClient's invoke, because the x-amzn-trace-id header already exists due to step (4)

Additional context

Add any other context about the PR here.

Checklist

• If you wrote E2E tests, are they resilient to concurrent I/O?
• If adding new public functions, did you add the @public tag and enable doc generation on the package?

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