Refactor Protobufs code

[shaobo-he-aws]

Description of changes:

There are two kinds of changes in this PR.

1. Added a function pureMergeFn such that pure (pure $ f) becomes pureMergeFn f.
2. Performed a best-effort formatting of match expressions.

[cdisselkoen]

Thanks for the attention to detail

[john-h-kastner-aws]

Looks better to me.

I will say that I don't personally like indenting the => arrow on matches to the same column. It looks nicer when reading the code, but it tends to require making changes to unrelated lines of code when adding a new match case or changing a pattern, making some diffs harder to understand and potentially creating merge conflicts. Wondering what other people think about this.