feat(tracer): adopted Utility class & updated unit tests

[dreamorosi]

Description of your changes

This PR introduces changes to the Tracer module to adopt the forthcoming Utility class that will be released in the @aws-lambda-powertools/commons package.

• Install released @aws-lambda-powertools/commons package
• Make changes to the code to use the Utility class
• Run unit & e2e tests
• Add note in the docs about initialising utility outside of function handler (ref)

How to verify this change

See the checks in the PR, see the screenshot below that shows a successful e2e test run (locally):

Optionally re-run the e2e tests on GitHub Actions.

Related issues, RFCs

#484
#547

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
• 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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[dreamorosi]

This PR is on hold until #547 is merged & released.

[ijemmy]

LGTM