[SR-3458] Collapse various collection wrappers using conditional conformance

[airspeedswift]

Previous ID	SR-3458
Radar	rdar://problem/31411207
Original Reporter	@airspeedswift
Type	Improvement
Status	Resolved
Resolution	Done

Additional Detail from JIRA

Votes	0
Component/s	Standard Library
Labels	Improvement, AffectsABI, swift-evolution-proposal-needed
Assignee	@airspeedswift
Priority	Medium

md5: c511734b8d422b61a3127634ab25d21c

Issue Description:

The conditional conformance feature from the generics manifesto, slated for Swift 4, enables the collapsing of a number of different wrapper types over bidirectional and random access collections in the standard library to be collapsed into single types:

• LazyFilter*Collection should be collapsed into LazyFilterCollection

• LazyMap*Collection should be collapsed into LazyMapCollection

• *Slice should be collapsed into Slice

• Default*Indices should be collapsed onto DefaultIndices

• Reversed*Collection should be collapsed onto ReversedCollection

This would resolve ABI FIXMEs #27, 42, 45, 59, 66, 75

[bob-wilson]

@swift-ci create

[bob-wilson]

This is done in #12913

We will track Lazy and Range refactorings separately.