Do not implement persisting analysis results to disk

[matklad]

This is an issue to document a negative design decision.

Originally I've envisioned saving analysis results to disk, to improve start up time. However, after reading rust-lang/rfcs#1317 (comment) I am no convinced that it's better to keep away from disks unless we are absolutely pressed.

• it is a ton of complexity
• we should make analysis lazy enough and compact enough such that keeping stuff in memory is not too much of a burden.

[matklad]

We don't have persistence anyway, so closing as fixed :D