fix: Update tag setting to use addEnvironment API

[samchungy]

What does this PR do?

Resolves #596

Motivation

My CI is broken: https://github.com/seek-oss/skuba/actions/runs/25618922361/job/75201906880

Testing Guidelines

• I updated aws-cdk-lib to the problematic version and ran yarn test.
• I also used the previous version of aws-cdk-lib, reverted my test changes and ran yarn test to verify backwards compatibility

Additional Notes

Unlike the other PRs, this isn't vibe coded...

This PR handles both older versions of aws-cdk-lib and newer versions but if you'd prefer a cleaner interface you can view the breaking change alternative here: #601

Types of Changes

• Bug fix
• New feature
• Breaking change
• Misc (docs, refactoring, dependency upgrade, etc.)

Check all that apply

• This PR's description is comprehensive
• This PR contains breaking changes that are documented in the description
• This PR introduces new APIs or parameters that are documented and unlikely to change in the foreseeable future
• This PR impacts documentation, and it has been updated (or a ticket has been logged)
• This PR's changes are covered by the automated tests
• This PR collects user input/sensitive content into Datadog

[samchungy]

Sorry I'm not too sure how to use projen - not sure how to bump the dev dep but keep the peer dep the same version

[TalUsvyatsky]

Thanks for opening this PR, this was ultimately resolved with #601 and https://github.com/DataDog/datadog-cdk-constructs/releases/tag/v2-4.0.0