Feature Request: Find all context

[pwrmiller]

Previously, all users of constructs would have to know beforehand the keys in the context to expect, and use either tryGetContext or getContext to retrieve a specific key from context.

I would suggest that we provide a mechanism to get the full context of a node in the construct tree, with overridable defaults.

[pwrmiller]

Implementation, and tests around this can be found here: #1751