Removes internal files used for swift demangling and replaces with package dependency on swift-demangling

[atreat]

Updates to use Swift Demangling package instead of managing this dependency inside this repo.

[ArielDemarco]

Have you tried to compile on the other platforms? (watchOS / macOS / etc)

[atreat]

Have you tried to compile on the other platforms? (watchOS / macOS / etc)

Good call, probably need to edit the Mac.xcworkspace and WatchOS.xcworkspace. Will confirm

[atreat]

Looks like the Mac.xcworkspace and WatchOs.xcworkspace don't compile even on master.

[ArielDemarco]

I expressed myself wrong: i'd check if this compiles on the different platforms we support on 6.x (like, integrating it with Embrace and check if it keeps working)