Support `condition` in Shared Resources DSL

[Kuchitama]

Summary

Support cloudformation's Condition Functions

Motivation

Sometimes we'd like to use Condition Functions to create shared resources. https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/intrinsic-function-reference-conditions.html

Guide-level explanation

Reference-level explanation

Drawbacks

Unresolved Questions