[teo1747]

Contains #42 and #43 as its base: merge them first, after which this diff shows only the statistics.

Completes KRN-WQ-011, whose trace records already existed (A52) but whose statistics did not.

• CONFIG_EMB_WORKQ_STATS is off by default.
• emb_workq_get_stats() fills emb_workq_stats_t:
  • the worst submit-to-start latency;
  • the longest handler and its function;
  • the items queued now and the most queued at once.
• emb_workq_reset_stats() restarts the maxima; the pending maximum restarts from the items queued now.
• Both are thread isr and O(1), with new API IDs 143 and 144 (registry regenerated).
• Times are kernel-clock ticks. A submit while the handler runs starts the latency of the run it queues, and flush markers are not items. Each work item gains a submit timestamp when the option is on.
• A65 records the contract.

Evidence

• New conformance case workq_stats_record_depth_latency_and_longest_handler.
  • It runs on native-timeslice, which now also builds this option.
  • Also passed under QEMU Cortex-M4 with EMB_SET=EMB_WORKQ_STATS=y, where real-time slack applies.
• Local runs, all passing: native gcc/clang/release/tiny/periodic/timeslice/timeslice-tickless, cm4-an386, rv32-virt and avr-uno.
• Checks: generate --check, the fault/storage/toolchain/kconfig/evidence tests, check_bounds and check-banned are clean; the docs build has the 9 known shim warnings.

Docs

KRN-WQ-011, SPEC-006 §7, STATUS, CHANGELOG, the configuration guide and the tasks guide.