128-bit core binary integer support

[oscbyspro]

I have implemented the I128 and U128 core binary integer models on a private branch, but the Swift.Int128 and Swift.UInt128 models fail some tests. I've submitted the following pull request(s) to unblock this feature:

• Fix recoverable [U]Int128 division-by-zero swiftlang/swift#77854
• [6.1][stdlib] Fix recoverable [U]Int128 division-by-zero swiftlang/swift#78045