### What does this PR do?
Hopefully fix https://github.com/oven-sh/bun/issues/21879
### How did you verify your code works?
Added a test with a seed larger than u32.
The test vector is from this tiny test I wrote to rule out upstream zig
as the culprit:
```zig
const std = @import("std");
const testing = std.testing;
test "xxhash64 of short string with custom seed" {
const input = "";
const seed: u64 = 16269921104521594740;
const hash = std.hash.XxHash64.hash(seed, input);
const expected_hash: u64 = 3224619365169652240;
try testing.expect(hash == expected_hash);
}
```
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