Minimize binary size

[sanity]

Implement relevant suggestions here: https://github.com/johnthagen/min-sized-rust

[iduartgomez]

I think this is more important for the contracts themselves (and then the contracts have to enable such optimizations), or for certain architectures/OS (mobile) maybe but otherwise is probably a good idea to optimize for speed still. We can check this again when we start working on mobile stuff I guess.

[github-actions]

Pivotal Tracker story: https://www.pivotaltracker.com/story/show/184207192