[6.0] performance improvements for Duration static members

[stephentyrone]

Explanation: New implementation of .seconds ... .nanoseconds that do not use 128b integers and therefore can be marked inlinable for specialization purposes. Also allow clocks to create durations directly without going through generic machinery. Scope: Library change only effecting Clocks and Duration. Original PR: https://github.com/apple/swift/pull/73419 and https://github.com/apple/swift/pull/73429 Risk: Low. Isolated library changes in routines that are easily tested. Testing: Normal swift tests cover these operations already. Reviewer: @lorentey @phausler

[stephentyrone]

@swift-ci test