Support array parsing with length using binary expression and parenthesis

[sryoya]

Requested feature
Mockgen should be able to parse an array using a binary expression or parenthesis in its length. They are not parsed correctly yet.
e.g. [1 + 2]int, [(2)]int

Why the feature is needed
As they are available expressions in the Go specifications, Mockgen should be able to handle them.

(Optional) Proposed solution A clear description of a proposed method for
More work needs to be done on the changes were made in #520 and #569

[sryoya]

@codyoss I already have the change ready in my local. As soon as you give me the go-ahead, I can get you a PR 👋