[stdlib] Fix FloatingPoint.init(exactly:)

[natecook1000]

This is another attempt at fixing this initializer — #11311 had to be reverted after a test failure that didn't show up during CI.

[natecook1000]

Please test with following pull request:
apple/swift-corelibs-foundation#1293

@swift-ci Please test

[swift-ci]

Build failed
Swift Test OS X Platform
Git Sha - 3870091

[swift-ci]

Build failed
Swift Test Linux Platform
Git Sha - 3870091

[natecook1000]

Please test with following pull request:
apple/swift-corelibs-foundation#1293

@swift-ci Please test

[natecook1000]

Please test with following pull request:
apple/swift-corelibs-foundation#1293

@swift-ci Please test Linux platform

[swift-ci]

Build failed
Swift Test Linux Platform
Git Sha - f3a5af8

[natecook1000]

Please test with following pull request:
apple/swift-corelibs-foundation#1293

@swift-ci Please test Linux platform

[natecook1000]

@gparker42 What do you think? I think the issue last time was that smoke tests don't run the 32-bit simulator tests—this should be in a better state.

[gparker42]

That sounds plausible. I see that the tests here ran on watchOS simulator which should cover 32-bit.

The only difference between this and #11311 is test changes, correct?

[natecook1000]

That's right—it's just what's in that last commit.

[gparker42]

Thanks, Nate.