Make Show instances produce valid Haskell and fix their uses

Clarification and motivation

Quoting once again from #742 (closed):

There's an unwritten expectation that the output of show should be a string you can copy-paste back into the editor.

While working on that issue however some issues with other Show instances have been noted.

We should fix them, in particular making sure that:

• whenever possible (aka where #752 (closed) doesn't apply), Show instance should match the expectation above
• Show instances shouldn't be expected to perform, nor be used for, pretty-printing (that's for Buildable), printing of valid Michelson (that's for RenderDoc)
• when not derived (for "enhancement" of the output, e.g. to show type annotations), they should support proper paren-wrapping (see showsPrec)

Acceptance criteria

1. Show instances produce valid Haskell code wherever possible, including parenthesis depending on context
2. uses of Show instances that rely on them producing pretty-printed text or valid Michelson are replaced to use Buildable and RenderDoc, respectively