[SR-14412] swift-corelibs-foundation’s firstRange(of:in:) and lastRange(of:in:) do not mirror macOS Foundation behavior when searched data is empty

[Frizlab]

Previous ID	SR-14412
Radar	None
Original Reporter	@Frizlab
Type	Bug

Environment

macOS: 11.2.3 (20D91), Swift version 5.3.2 (swiftlang-1200.0.45 clang-1200.0.32.28)

Linux: Docker image 2510a162d49e, Swift version 5.3.3 (swift-5.3.3-RELEASE)

Additional Detail from JIRA

Votes	0
Component/s	Foundation
Labels	Bug
Assignee	None
Priority	Medium

md5: e510ad147fb65e09109745e2fddd9fdd

Issue Description:

On macOS, with an empty searched data, `nil` is returned; on Linux (swift-5.3.3-RELEASE), an empty Range is returned.

I submitted a PR to mirror macOS’s behavior: #2992