chore(codebuild): remove deprecated Ubuntu 14.04 and Win 2016 Base images

[ashrafee-dev]

Issue # (if applicable)

Partially addresses #36342

Reason for this change

CDK v1 is end-of-life. The deprecated CodeBuild image constants (UBUNTU_14_04_* and WIN_SERVER_CORE_2016_BASE) are legacy v1 holdovers that are already excluded from the generated jsii output. Their implementation remains in the source, but they are no longer part of the public library surface. This change removes that leftover code now that v1 compatibility is no longer needed.

Description of changes

This PR removes deprecated CodeBuild image constants that were previously kept only for v1 compatibility:

• Removed 29 UBUNTU_14_04_* constants from LinuxBuildImage in packages/aws-cdk-lib/aws-codebuild/lib/project.ts
• Removed WIN_SERVER_CORE_2016_BASE from WindowsBuildImage in packages/aws-cdk-lib/aws-codebuild/lib/project.ts
• Updated packages/@aws-cdk-testing/framework-integ/test/aws-codepipeline-actions/test/integ.pipeline-ecs-deploy.ts to replace UBUNTU_14_04_DOCKER_17_09_0 with STANDARD_7_0
• Updated packages/aws-cdk-lib/aws-codebuild/test/codebuild.test.ts to remove references to WIN_SERVER_CORE_2016_BASE
• Removed the corresponding entries from deprecated_apis.txt
• Removed the corresponding rows from DEPRECATED_APIs.md

These APIs were already excluded from jsii output through deprecated_apis.txt. Removing them from the source and deprecated API listings completes the cleanup and aligns with the incremental deprecation-removal approach.

Describe any new or updated permissions being added

N/A — no new or updated IAM permissions are required.

Description of how you validated changes

• Ran the relevant CodeBuild unit tests
• Ran the related integration test(s)
• Ran build/synth tooling to confirm the package still builds successfully

Checklist

• My code adheres to the CONTRIBUTING GUIDE and DESIGN GUIDELINES

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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

[github-actions]

⚠️ Experimental Feature: This security report is currently in experimental phase. Results may include false positives and the rules are being actively refined.
Please try merge from main to avoid findings unrelated to the PR.

---

	Tests	Passed ☑️	Skipped	Failed ❌️
Security Guardian Results	24 ran	23 passed		1 failed

Test	Result
Security Guardian Results
packages/@aws-cdk-testing/framework-integ/test/aws-codepipeline-actions/test/integ.pipeline-ecs-deploy.js.snapshot/aws-cdk-codepipeline-ecs-deploy.template.json
iam-no-overly-permissive-passrole.guard	❌ failure

• View Security Guardian Results

[github-actions]

⚠️ Experimental Feature: This security report is currently in experimental phase. Results may include false positives and the rules are being actively refined.
Please try merge from main to avoid findings unrelated to the PR.

---

	Tests	Passed ☑️	Skipped	Failed ❌️
Security Guardian Results with resolved templates	24 ran	22 passed		2 failed

Test	Result
Security Guardian Results with resolved templates
packages/@aws-cdk-testing/framework-integ/test/aws-codepipeline-actions/test/integ.pipeline-ecs-deploy.js.snapshot/aws-cdk-codepipeline-ecs-deploy.template.json
iam-no-overly-permissive-passrole.guard	❌ failure
iam-role-root-principal-needs-conditions.guard	❌ failure

• View Security Guardian Results with resolved templates