Derive `Show' instance for parameter of upgradeable contract and Void_

Description

Problem: the standard Parameter of the standard upgradeable contract does not have Show instance which is sometimes useful (e. g. for debugging purposes). Also Void_ does not have it, but it seems useful as well.

Solution: derive instances in a stock way.

Related issue(s)

None

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  • If I added new functionality, I added tests covering it ← not really, but we trust stock deriving
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