Use `LeanApplier` for all Rewrites?

[marcusrossel]

Right now we use the LeanApplier only for rewrites coming from Lean, but not those hardcoded by us in Rust. This might cause problems because that means that we don't get capture avoidance, etc. for those rewrites.

[marcusrossel]

We'd have to take care not to disable rewrites on primitive constructors in that case.