test-case: latency-metrics: introduce latency tests

[golowanow]

Introduce latency tests using JACK Audio Connection Kit:
run jackd audio service, connect ports with loopback and run jack_iodelay to collect latency measurements, calculate and save statistics in a json report file.

[marc-hb]

Minor code style suggestions, all the rest LGTM.

Some audio expert must review the actual logic, I did not.

[golowanow]

25/May changes:

• detect and report xruns;
• some renames for better integration with CI;
• coding style improvements.

[golowanow]

26/May changes (should be the last significant change in this PR):

• add ALSA pcm-s parameters to run on SDW.
• add 'trial' mode: repeat latency measurements gradually reducing buffer size (frames) to find the smallest latency achievable.
• set alsa parameters to the same as check-alsabat.sh does.
• allow to set a max number of ignored 'xruns' (per each run).
• run mode with loopback set at the JACK to estimate its latency.

[golowanow]

27/May changes:
after more experiments with 'trial' mode and reproduceable xrun's, I've recognized that these errors are actually from jackd, and it needs its own log parser (in the very early versions of this test jackd and iodelay had the same output stream).

[marc-hb]

Again, some audio expert should review the logic.

[golowanow]

28/May changes - address review comments:

• keep command line pieces in arrays for better control on expansion;
• use printf instead of echo;

[marc-hb]

LGTM, some audio expert must review.

[kv2019i]

Thanks @golowanow , looks great! Good comments in code, this will be good basis to build on other tests.

[golowanow]

SOFCI TEST