Remove Objective-C compatibility; adopt Swift language features

[JThramer]

No man is an island,
Entire of itself.
Each is a piece of the continent,
A part of the main.
If a clod be washed away by the sea,
Europe is the less.
As well as if a promontory were.
As well as if a manor of thine own
Or of thine friend's were.
Each man's death diminishes me,
For I am involved in mankind.
Therefore, send not to know
For whom the bell tolls,
It tolls for thee.
-- For Whom The Bell Tolls, by John Donne

Work in progress.

Running Checklist:

• Eliminate Objective-C support
  • Delete @objc attributes and MB class prefixes
  • Fix resultant build errors.
  • Delete methods whose sole purpose is to bridge to Objective-C
  • Fix broken Guidance Cards
  • Fix any other test failures
  • Move enumeration declarations from Objective-C headers to Swift files
  • Delete CMapboxDirections target from SPM distribution of MapboxDirections.swift
  • Remove references to Objective-C compatibility from readmes and jazzy guides
• Take advantage of Swift language features
  • Convert value classes to structures or enumerations with associated types
  • Convert abstract classes to protocols with default implementations
  • Move global variables and global constants under structures and classes
• Replace magic default values with optionals

Fixes #2231.

[JThramer]

Some lessons learned so far:

There are a few unanticipated complications that may impact our refactoring objectives. Namely:

• KVO is only possible through NSObject Inheritance (OBJC Dynamic Dispatch), and that affects classes like RouteProgress and NavigationSettings.
• UIAppearance inherits from NSObjectProtocol, which pins Style.swift and DayStyle.swift to our current implementation without refactoring our theming mechanism.

[1ec5]

This test should be restored and fixed.

[1ec5]

I got a crash arriving at the final destination:

#0	0x00007fff518292c6 in __pthread_kill ()
#1	0x00007fff518d0bf1 in pthread_kill ()
#2	0x00007fff517b9a3c in abort ()
#3	0x00000001080e09e5 in swift::fatalError(unsigned int, char const*, ...) ()
#4	0x00000001080d8de7 in swift::swift_dynamicCastFailure(void const*, char const*, void const*, char const*, char const*) ()
#5	0x00000001080d8e5a in swift::swift_dynamicCastFailure(swift::TargetMetadata<swift::InProcess> const*, swift::TargetMetadata<swift::InProcess> const*, char const*) ()
#6	0x00000001080dafd3 in swift_dynamicCastClassUnconditional ()
#7	0x0000000105e780c3 in closure #1 in RouteMapViewController.endOfRouteViewController.getter at /path/to/mapbox-navigation-ios/MapboxNavigation/RouteMapViewController.swift:20
#8	0x0000000105e77f07 in RouteMapViewController.endOfRouteViewController.getter at /path/to/mapbox-navigation-ios/MapboxNavigation/RouteMapViewController.swift:18
#9	0x0000000105e85928 in RouteMapViewController.embedEndOfRoute() at /path/to/mapbox-navigation-ios/MapboxNavigation/RouteMapViewController.swift:363
#10	0x0000000105e86497 in RouteMapViewController.showEndOfRoute(duration:completion:) at /path/to/mapbox-navigation-ios/MapboxNavigation/RouteMapViewController.swift:384
#11	0x0000000105e31c41 in NavigationViewController.showEndOfRouteFeedback(duration:completionHandler:) at /path/to/mapbox-navigation-ios/MapboxNavigation/NavigationViewController.swift:539
#12	0x0000000105e319f9 in NavigationViewController.navigationService(_:didArriveAt:) at /path/to/mapbox-navigation-ios/MapboxNavigation/NavigationViewController.swift:532
#13	0x0000000105e32ca9 in protocol witness for NavigationServiceDelegate.navigationService(_:didArriveAt:) in conformance NavigationViewController ()
#14	0x0000000107c75cfd in MapboxNavigationService.router(_:didArriveAt:) at /path/to/mapbox-navigation-ios/MapboxCoreNavigation/NavigationService.swift:464
#15	0x0000000107c76529 in protocol witness for RouterDelegate.router(_:didArriveAt:) in conformance MapboxNavigationService ()
#16	0x0000000107c63425 in RouteController.updateRouteLegProgress(status:) at /path/to/mapbox-navigation-ios/MapboxCoreNavigation/RouteController.swift:275

The error is:

2019-11-12 19:05:27.940108-0800 Example-CarPlay[43862:4033688] [Storyboard] Unknown class MBEndOfRouteViewController in Interface Builder file.

Please audit the storyboards for any Objective-C class names.

Serious crashes due to stale references in storyboards.