feat(synthetics): latest canary runtimes for NodeJS, Python (#29132)

Closes #29135

### Reason for this change

Surface latest runtime versions in CDK. Older runtimes are being deprecated March 19, 2024

> To ensure uninterrupted canary runs and continued monitoring, AWS recommends customers to update their canaries to the latest Synthetics Runtimes versions: syn-nodejs-puppeteer-6.2 or higher for NodeJS-18, syn-nodejs-puppeteer-5.2 or higher for NodeJS-16, and syn-python-selenium-2.1 or higher for Python [2]. Canaries updated with latest Synthetics runtimes will continue running without interruption and receive future Lambda security updates.

### Description of changes

- feat(synthetics): add 5.2, 6.1, 6.2 nodejs runtimes, deprecate 3.x runtimes
- feat(synthetics): add syn-python-selenium-2.1 runtime
- test(synthetics): update integration tests to cover latest runtimes

### Description of how you validated changes

Attempted to run integration tests, but I don't have appropriate account setup

### Checklist
- [x] My code adheres to the [CONTRIBUTING GUIDE](https://github.com/aws/aws-cdk/blob/main/CONTRIBUTING.md) and [DESIGN GUIDELINES](https://github.com/aws/aws-cdk/blob/main/docs/DESIGN_GUIDELINES.md)

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*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*