[llvm-debuginfod] Switch to xxh3_64bits

[MaskRay]

Summary

Many sources show that xxh3 is much better than xxh64. This particular
instance may or may not have noticeable difference, but this change
moves us toward removing xxHash64.

This change will invalid cache and I haven't fixed the tests.
I just want to post the patch first to seek for opinions:)

[MaskRay]

fix tests

[jhenderson]

I think the change makes sense, but I don't really know anything about debuginfod, so can't really be confident.

[MaskRay]

@gulfem @mysterymath :)

llvm/lib/Debuginfod/Debuginfod.cpp

 
 #include <atomic>
 #include <thread>
 
 namespace llvm {
 
 using llvm::object::BuildIDRef;
 
-static std::string uniqueKey(llvm::StringRef S) { return utostr(xxHash64(S)); }
+static std::string uniqueKey(llvm::StringRef S) { return utostr(xxh3_64bits(S)); }
 
 // Returns a binary BuildID as a normalized hex string.
 // Uses lowercase for compatibility with common debuginfod servers.
 static std::string buildIDToString(BuildIDRef ID) {
   return llvm::toHex(ID, /*LowerCase=*/true);
 }
 
 bool canUseDebuginfod() {