Consistent design for binary symbols

[topological-modular-forms]

Timothy Chow wrote:

There are three graph products that are closely related to each other: $G\times H$, $G\boxtimes H$, and $G\mathbin{\square}H$. [...] I think it would look nicer if the three symbols all had the same size (compare $\times\otimes$ with $\times\boxtimes$), which they currently don't.

I should be sure to make the size of all binary symbols consistent, including the ones above but also others, like $\diamond$.