Measure end to end latency

[pierd]

No description provided.

[pierd]

#1022 adds debug-local-datagram-latency feature for debugging the latency of sent unreliable messages, it relies on clocks being in sync so it works the best on localhost or via proxy (with both client and server running on the same machine).

[pierd]

Reopening as I'm going to explore adding true end to end latency (from user input to rendered frame).

[pierd]

Latency talk to watch: https://www.gdcvault.com/play/1025968/Controller-to-Display-Latency-in

[pierd]

Created a version in this branch: https://github.com/AmbientRun/Ambient/tree/kuba/timings

It currently spams the logs with all the measurements:

18:07:38  WARN ambient_timings: TIMING EVENT: Input 7.981000166s
18:07:38  WARN ambient_timings: TIMING EVENT: RenderingFinished 7.986576833s
18:07:38 ERROR ambient_timings: TIMINGS: Input <- 4.855708ms -> ScriptingStarted <- 10.20825ms -> ScriptingFinished <- 6.875µs -> ClientSystemsStarted <- 118.125µs -> ClientSystemsFinished <- 79.333µs -> DrawingWorld <- 379.709µs -> DrawingUI <- 144.083µs -> SubmittingGPUCommands <- 5.973875ms -> RenderingFinished
18:07:38 ERROR ambient_timings: INPUT TO RENDERED: 21.765958ms
18:07:38  WARN ambient_timings: TIMING EVENT: ScriptingStarted 7.986774625s
18:07:38  WARN ambient_timings: TIMING EVENT: ScriptingFinished 7.997007375s
18:07:38  WARN ambient_timings: TIMING EVENT: ClientSystemsStarted 7.997012041s
18:07:38  WARN ambient_timings: TIMING EVENT: ClientSystemsFinished 7.997129458s
18:07:38  WARN ambient_timings: TIMING EVENT: DrawingWorld 7.997216875s
18:07:38  WARN ambient_timings: TIMING EVENT: DrawingUI 7.997581333s
18:07:38  WARN ambient_timings: TIMING EVENT: SubmittingGPUCommands 7.997727625s
18:07:38  WARN ambient_timings: TIMING EVENT: RenderingFinished 8.002686125s
18:07:38 ERROR ambient_timings: TIMINGS: Input <- 5.774459ms -> ScriptingStarted <- 10.23275ms -> ScriptingFinished <- 4.666µs -> ClientSystemsStarted <- 117.417µs -> ClientSystemsFinished <- 87.417µs -> DrawingWorld <- 364.458µs -> DrawingUI <- 146.292µs -> SubmittingGPUCommands <- 4.9585ms -> RenderingFinished
18:07:38 ERROR ambient_timings: INPUT TO RENDERED: 21.685959ms
18:07:38  WARN ambient_timings: TIMING EVENT: ScriptingStarted 8.002881125s
18:07:38  WARN ambient_timings: TIMING EVENT: ScriptingFinished 8.013081083s
18:07:38  WARN ambient_timings: TIMING EVENT: ClientSystemsStarted 8.013087208s
18:07:38  WARN ambient_timings: TIMING EVENT: ClientSystemsFinished 8.0131955s
18:07:38  WARN ambient_timings: TIMING EVENT: DrawingWorld 8.013279083s
18:07:38  WARN ambient_timings: TIMING EVENT: DrawingUI 8.013685583s
18:07:38  WARN ambient_timings: TIMING EVENT: SubmittingGPUCommands 8.01383875s
18:07:38  WARN ambient_timings: TIMING EVENT: Input 8.014556708s
18:07:38  WARN ambient_timings: TIMING EVENT: RenderingFinished 8.019795416s
18:07:38 ERROR ambient_timings: TIMINGS: ScriptingStarted <- 10.199958ms -> ScriptingFinished <- 6.125µs -> ClientSystemsStarted <- 108.292µs -> ClientSystemsFinished <- 83.583µs -> DrawingWorld <- 406.5µs -> DrawingUI <- 153.167µs -> SubmittingGPUCommands <- 5.956666ms -> RenderingFinished
18:07:38  WARN ambient_timings: TIMING EVENT: ScriptingStarted 8.019980666s
18:07:38  WARN ambient_timings: TIMING EVENT: ScriptingFinished 8.030197583s
18:07:38  WARN ambient_timings: TIMING EVENT: ClientSystemsStarted 8.030206958s
18:07:38  WARN ambient_timings: TIMING EVENT: ClientSystemsFinished 8.030378958s

I need a decision on how to properly report it so that it's actually useful.