temporal conversion functions cannot work on negative input properly

[viirya]

Describe the bug

timestamp_ns_to_datetime(-1) gets "invalid or out-of-range datetime" error. Other functions expect to have same issue too.

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To Reproduce

#[test]
fn negative_input_timestamp_ns_to_datetime() {
  timestamp_ns_to_datetime(-1);
}

---- temporal_conversions::tests::negative_input_timestamp_ns_to_datetime stdout ----
thread 'temporal_conversions::tests::negative_input_timestamp_ns_to_datetime' panicked at 'invalid or out-of-range datetime', ...
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

Expected behavior

Additional context