Chore(tracer): unit tests to verify decorators await decorated class methods

[dreamorosi]

Description of your changes

In #1091 it was reported that the tracer.captureMethod() and tracer.captureLambdaHandler() decorators might not be awaiting correctly the decorated methods.

After a closer look it seems that they we already awaited properly, see:

• captureMethod here: https://github.com/awslabs/aws-lambda-powertools-typescript/blob/main/packages/tracer/src/Tracer.ts#L440
• captureLambdaHandler here: https://github.com/awslabs/aws-lambda-powertools-typescript/blob/main/packages/tracer/src/Tracer.ts#L367

This PR simply introduces unit tests to prove that this is the case and to guard against any future regressions.

How to verify this change

See existing & new unit tests passing.

Related issues, RFCs

Issue number: #1091

PR status

Is this ready for review?: YES
Is it a breaking change?: NO

Checklist

• My changes meet the tenets criteria
• I have performed a self-review of my own code
• I have commented my code where necessary, particularly in areas that should be flagged with a TODO, or hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding changes to the examples
• My changes generate no new warnings
• The code coverage hasn't decreased
• I have added tests that prove my change is effective and works
• New and existing unit tests pass locally and in Github Actions
• Any dependent changes have been merged and published in downstream module
• The PR title follows the conventional commit semantics

Breaking change checklist

N/A

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[ijemmy]

LGTM. Small suggestions on readability but will leave it up to you.

[dreamorosi]

LGTM. Small suggestions on readability but will leave it up to you.

Thank you @ijemmy, I have accepted both your suggestions.

[dreamorosi]

Going to merge this. @ijemmy's previously already approved the PR and left comments which were addressed, so I'm going to consider this as approved.