NSOrderedSet: Implement more functionality

[spevans]

• Add copy() and mutableCopy().

• Add .set and .array to return immumtable views of the current
  contents.

• Implement index(of:inSortedRange:options:usingComparator cmp:)
  by calling NSArray()'s version on ._orderedStorage.

• Implement description(withLocale:), description(withLocale:indent:),
  .description and .customMirror.

• NSCoding still needs to be implemented.

[spevans]

@swift-ci test

[spevans]

Note: Need to add some tests.

[millenomi]

Fixes https://bugs.swift.org/browse/SR-10405, https://bugs.swift.org/browse/SR-10406, https://bugs.swift.org/browse/SR-10407, https://bugs.swift.org/browse/SR-10408

[millenomi]

Can you use storage._swiftObject instead?

[spevans]

I looked at how NSArray and NSSet implemented copy and mutableCopy and didn't see the use of _swiftObject there. Is it needed even though the types of the Set and Array are Swift not CF Types?

[spevans]

@swift-ci test linux

[spevans]

@swift-ci test linux

[spevans]

@swift-ci test linux

[millenomi]

@swift-ci please test

[millenomi]

The idea here is that we're hitting a compiler bug around casting, which is often problematic while developing s-c-f because s-c-f is part of the implementation of casting itself (and also has to coexist with the bridging setup on Darwin.) The guideline going forward is to avoid bridging casts and use _swiftObject, _cfObject and _nsObject where they exist, and __SwiftValue.store(…)/.fetch(…) otherwise if all you have is an Any or AnyObject (which will do the right thing wrt interacting with bridged values coming from the ObjC Foundation on Darwin). This only applies to s-c-f's codebase; outside, including in TestFoundation, it is okay to use bridging as usual.

[spevans]

@swift-ci test

[spevans]

@swift-ci test