Ensure documentation coverage and clean up of the various APIs.

Fixes #1891


BREAKING CHANGE:
* **core:** `StackProps.autoDeploy` has been removed and replaced by `StackProps.hide` (with negated logic).
* **core:** `ISynthesizable.synthesize` now accepts an `ISynthesisSession` which contains the `CloudAssemblyBuilder` object.
* **cx-api:** Multiple changes to the cloud assembly APIs to reduce surface area and clean up.

BREAKING CHANGE:
- `StackProps.autoDeploy` renamed to `entrypoint` (still true by default).
- CLI must be upgraded to 0.34.0 (cx protocol changes)

…nstruct

BREAKING CHANGE:
* **core:** `node.validateTree` is now `ConstructNode.validate(node)`
* **core:** `node.prepareTree` is now `ConstructNode.prepare(node)`
* **core:** `node.getContext` is now `node.tryGetContext`
* **core:** `node.recordReference` is now `node.addReference`
* **core:** `node.apply` is now `node.applyAspect`
* **core:** `node.ancestors()` is now `node.scopes`
* **core:** `node.required` has been removed.
* **core:** `node.typename` has been removed.
* **core:** `node.addChild` is now private
* **core:** `node.findReferences()` is now `node.references`
* **core:** `node.findDependencieS()` is now `node.dependencies`
* **core:** `stack.dependencies()` is now `stack.dependencies`
* **core:** `construct.node.stack` is now `Stack.of(construct)`
* **core:** `CfnElement.stackPath` has been removed.

BREAKING CHANGE:
* **core:** `node.resolve` has been moved to `stack.resolve`.
* **core:** `node.stringifyJson` has been moved to `stack.stringifyJson`.

* stringifyJson => toJsonString
* node.resolve => stack.resolve
* CloudFormationLang is now toJsonString

…nstruct