Add support for collections and dictionaries of input

[bobhauser]

Implemented the ability specify collections and dictionaries of Inputs on activities.

For example:
public List<Input<string>>? Recipients { get; set; } = default;
public Dictionary<string, Input<string>>? Arguments { get; set; } = default;

See #5421 for more details.

This change is not breaking in any way, and all existing tests pass.

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This change is 

[bobhauser]

@dotnet-policy-service agree company="Kinaxis"

[bobhauser]

Please let me know if you have any concerns with this change.