Revert "Use VersionTuple for parsing versions in Triple. This makes it...

Revert "Use VersionTuple for parsing versions in Triple. This makes it possible to distinguish between "16" and "16.0" after parsing, which previously was not possible."

This reverts commit 1e828646.

llvm/test/Transforms/LoopStrengthReduce/X86/2009-11-10-LSRCrash.ll fails
with assertion failure:

llc: /home/nikic/llvm-project/llvm/include/llvm/ADT/Optional.h:196: T& llvm::optional_detail::OptionalStorage<T, true>::getValue() & [with T = unsigned int]: Assertion `hasVal' failed.
...
 #8 0x00005633843af5cb llvm::MCStreamer::emitVersionForTarget(llvm::Triple const&, llvm::VersionTuple const&)
 #9 0x0000563383b47f14 llvm::AsmPrinter::doInitialization(llvm::Module&)