(docs): nodejs-function, document how to disable bundling for tests

Create an option to disable, (or automatically disable?) asset build/bundling, when using Jest to instantiate a cdk-pipeline for tests

### Use Case

When using a pipeline instance in jest it causes the assets to build/bundle, it may be the intention of the test to check only that the pipeline is correctly formed, build/bundle testing may be handled else where.
In this case the build/bundle process creates additional time delay on testing in synth stage of the pipeline.

### Proposed Solution

Create an option to disable, (or automatically disable?) asset build/bundling, when using Jest to instantiate a cdk-pipeline for tests

### Other

* [ ] :wave: I may be able to implement this feature request
* [ ] :warning: This feature might incur a breaking change

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This is a :rocket: Feature Request

Start with the Jest tests that instantiate a cdk-pipeline and trace where nodejs-function assets are built or bundled during synthesis. Resolve whether disabling bundling should be explicit or automatic, then document and verify that pipeline-shape tests avoid bundling while bundling tests still exercise it.

Written by the indexing model from the issue text.