pass: optimise away array get->put

[ss2165]

In guppy it is common to do things like

q = array(qubit(), qubit())
h(q[0])
x(q[0])

This lowers to get from array -> unwrap option -> do thing -> construct option -> put back in array -> get from array.
This results in a lot of LLVM bloat.

It would be better to defer the "put back in array" until as late as possible.

This may be easier once Guppy has a dedicated array extension. CQCL/guppylang#628