[SR-3752] Remove redundant word "Index" from Collection properties/typealiases

[airspeedswift]

Previous ID	SR-3752
Radar	rdar://problem/29976316
Original Reporter	@airspeedswift
Type	Improvement

Additional Detail from JIRA

Votes	0
Component/s	Standard Library
Labels	Improvement, AffectsABI, StarterProposal
Assignee	None
Priority	Medium

md5: 0c809e36d2916cefa628bdb99c61a0e8

Issue Description:

The two properties "startIndex" and "endIndex", and the typealias IndexDistance should have the word "Index" removed, in order to reduce clutter. The meaning is clear without it.

For source compatibility reasons, deprecated computed properties or a typealias should be provided.

[swift-ci]

Comment by Vijaya Prakash Kandel (JIRA)

Is it okay if i take this task? Any pointers or direction is appreciated.

PS., this is my first comment on the bug tracker. And so my first task.