fix: AWS CDK legacy exports

[dytyniuk]

This PR fixes the following issues:

• Deprecation of legacy exports from AWS CDK CLI pacakge #116
• cdklocal bootstrap does not respect AWS_ENDPOINT_URL variable #103

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A little context for the proposed changes

I have spent at least several hours setting up the environment to point the vanilla AWS CDK CLI to LocalStack.
I have checked the changelogs for the AWS SDK for JavaScript, the AWS CDK CLI, and LocalStack.
And I want to share what I think the way for aws-cdk-local is:

1. There's no need to patch the AWS SDK instance within AWS CDK CLI because it now runs the aws-sdk-js v3 that respects environment variables just like AWS CLI does.
2. LocalStack deprecated Lambda source code mounts, so there's no need to hack it anymore. And, cdk(local) watch --hotswap, IMHO, is a more convenient alternative.
3. The latest version of AWS CDK CLI (as of 2026/03/06) is 2.1109.0, so supporting AWS CDK versions prior to v2.14 is irrational.

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Tested against LocalStack running in Docker:

$ printenv | grep AWS
$ docker ps
CONTAINER ID   IMAGE                          COMMAND                  CREATED          STATUS                    PORTS                                                          NAMES
90529edf6b13   localstack/localstack:stable   "docker-entrypoint.sh"   20 minutes ago   Up 15 seconds (healthy)   127.0.0.1:4510-4559->4510-4559/tcp, 127.0.0.1:4566->4566/tcp   localstack-main
$ awslocal s3 ls
$ cdklocal bootstrap
 ⏳  Bootstrapping environment aws://000000000000/us-east-1...
Trusted accounts for deployment: (none)
Trusted accounts for lookup: (none)
Using default execution policy of 'arn:aws:iam::aws:policy/AdministratorAccess'. Pass '--cloudformation-execution-policies' to customize.
CDKToolkit: creating CloudFormation changeset...
 ✅  Environment aws://000000000000/us-east-1 bootstrapped.
$ awslocal s3 ls
2026-03-07 21:12:33 cdk-hnb659fds-assets-000000000000-us-east-1