Simplify RttSample by merging signed and unsigned fields into a single SignedDuration for adjusted and effective RTT. This ensures accurate reporting and statistics when server processing time exceeds raw RTT.
Simplify the statistics model by merging signed and unsigned duration types into a single structure that uses i128 to consistently handle both positive and negative time offsets.
Rename system_time_ns to unix_time_ns_after_epoch for better clarity on output behavior and update a continuous mode test case name to more accurately reflect its purpose.