Use the new inline ViewEnvironmentKey function where possible.

[rjrjr]

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It didn't have to be a function, it's just a convenience that makes it easier to implement ViewEnvironmentKey, should have written it two years ago. I'd like to make a pass and use it universally after this merges.

Originally posted by @rjrjr in https://github.com/square/workflow-kotlin/pull/712#discussion_r839949333