Gridify is slow

[khieta]

This proof about controlled gates commuting is horribly slow (about 10 mins on my machine). Can we reorder the rewrite rules in gridify, or manually "gridify" this term to improve performance?

[khieta]

(Assigned @rnrand in case he's looking for a way to waste time.)

[k4rtik]

This commit e2931dd admitting the proof (albeit not ideal) makes it faster for now.