feat!: raise CDK and Node minimums for native references

[garysassano]

Reason for this change

Native weak cross-stack ACM references require a newer CDK and jsii toolchain. This PR isolates the library-wide compatibility change from the certificate construct in #82.

Description of changes

• Raise the minimum aws-cdk-lib to 2.268.0, constructs to 10.8.1, and Node.js to 22; move jsii and TypeScript to 6.
• Update CI Node versions and the FSx KMS reference API for the new CDK version.
• Update @aws-cdk/integ-runner to 2.205.3 and remove the duplicate ts-jest declaration.
• Keep Jest at one worker because an uncapped full build exhausted WSL memory.

Breaking change: Existing consumers on older CDK, constructs, or Node versions must upgrade before adopting a release containing this PR.

Description of how you validated changes

• npx projen and npm run compile passed on this branch.
• npx jest --runInBand --no-coverage test/aws-fsx/ontap-file-system.test.ts passed 71 tests on the child branch with these foundation files unchanged.
• The full build is unverified. A trial with the Jest cap removed exhausted WSL memory; the cap is restored. Upstream build CI still requires maintainer approval for this fork. Maintainer action needed: please approve the build workflow run for this PR.

Checklist

• My code adheres to the CONTRIBUTING GUIDE
• My pull request adheres to the Pull Request Rule

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