* constructor codegen
* Update string_cache to 0.7
* make swc_common not depend on sourcemap
* Remove unused dependencies
* update either to 1.5.0
* update rustc-ap crates to 297
* remove unused dependency (fnv)
common:
- rename `Folder` to `Fold`
- folder.then()
- impl Fold for Box<F>
- impl Fold<T> for &mut F where F: Fold<T>
transforms:
- make Simplifier private
- organize compat
codegen:
- use `Mark` to avoid deoptimization
swc:
- upgrade rayon and use global thread pool instead