(custom-resources): AwsCustomResource has an unnecessary risk of responses being too large

[rix0rrr]

Describe the bug

Observed in #28108 (temporary fix: #28112)

The AwsCustomResource custom resource posts the entire response object to CloudFormation, which can exceed the maximum size of a response object.

The workaround that has been invented previously is to have the user declare using outputPaths exactly what paths to include in the response so that we can stay within the maximum size.

This puts a burden on the user that is fully unnecessary: the AwsCustomResource can know beforehand exactly which fields are required, because it knows exactly what resource.getAttString() calls are being expected of it.

This behavior should be automatic, and not come down to user input (because users will forget, which will lead to the linked issue).

Expected Behavior

AwsCustomResource should determine its fields to respond automatically.

Current Behavior

The construct library author needs to remember that responses can become too large, and when they add a call to resource.getAttString() they have to remember to update outputPaths in the custom resource.

Reproduction Steps

Possible Solution

We should fill the list of outputPaths automatically from the calls to getAttString().

The outputPaths property should become a single top-level property, and be removed from the AwsApiCall structure as well. It doesn't make sense that the values can be different for CREATE and UPDATE, that's not how CloudFormation works.

Additional Information/Context

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TypeScript

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