fix(cx-api): cannot detect CloudAssembly across different libraries

[mrgrain]

Reason for this change

We are publishing the cx-api package twice: Once as a standalone package @aws-cdk/cx-api and once as part of the construct library under aws-cdk-lib/cx-api. The code is copied during the release and the same versions of the packages will have the same code.

However this makes it difficult for other packages to take a type dependency on types from this package. The most common class that's used from cx-api is CloudAssembly - the result of app.synth(). Previously a package had to take a dependency on the very large aws-cdk-lib just to use a single type. It would be better if other packages could instead depend on the smaller, much more focused @aws-cdk/cx-api package.

Description of changes

This adds the same mechanism to CloudAssembly to detect cross-library compatibility, that we already use for constructs like Stack or App. In TypeScript, it's now possible for a consuming package to receive an object from either package and check at runtime if it satisfies the requirements.

We cannot get around type checking with this. Instead we introduce a new type ICloudAssembly into the Cloud Assembly Schema package (cdklabs/cloud-assembly-schema#133). This interface only declares a single property: directory. Consumers can use this type to indicate where they would like to receive a CloudAssembly. They can then use runtime code to either confirm a provided object already satisfies the requirements or fallback to creating a new CloudAssembly from the directory.

Because the CloudAssembly in cxapi implements the new interface, this approach will work in all jsii languages. In TypeScript it's even compatible with older version of aws-cdk-lib. Jsii language will only support this going forward.

Describe any new or updated permissions being added

n/a

Description of how you validated changes

Unit tests.

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

[aws-cdk-automation]

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.44%. Comparing base (ebe9580) to head (ed53139).
Report is 3 commits behind head on main.

Additional details and impacted files

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Flag	Coverage Δ
suite.unit	81.44% <ø> (ø)

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Components	Coverage Δ
packages/aws-cdk	80.81% <ø> (ø)
packages/aws-cdk-lib/core	82.10% <ø> (ø)

[aws-cdk-automation]

AWS CodeBuild CI Report

• CodeBuild project: AutoBuildv2Project1C6BFA3F-wQm2hXv2jqQv
• Commit ID: ed53139
• Result: SUCCEEDED
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