feat(controller): compute the LSF CPU peak and efficiency fields (bug-1736)

update_job_cpu_stats() (misc.c), run after each usage report:
- each host's cpu_rate = CPU-seconds gained / wall seconds since its
  previous report; the job's cores = the sum over hosts
- peak_cpu = highest job cores seen (peak_cpu_time = it rounded, the
  wire field is an integer); peak_cpu_duration = the interval that set it
- avg_cpu_efficiency = cpu_time / elapsed / slots, peak_cpu_efficiency =
  peak_cpu / slots, mem_efficiency = highest used_mem / rusage[mem]
  request (job-wide total, per task by default), all in percent
aggregate_job_runusage() no longer treats cumulative cpu_time as a peak.

New fields host sample_time/cpu_rate and job peak_cpu are appended to
the capnp structs (old WAL entries still decode) and copied by
merge_job_runusage(), so a promoted standby keeps the rate baselines.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

src/controller/testsuite/test_commit_barrier_reply.c

@@ -198,6 +198,11 @@ int update_pids(job_pidinfo_t **i, int n, int *p)
 int update_pgids(job_pidinfo_t **i, int n, int *p)
 { (void)i; (void)n; (void)p; return 0; }
 void aggregate_job_runusage(xce_job_runusage_t *r) { (void)r; }
+void update_job_cpu_stats(xce_job_runusage_t *r, const char *h, int p,
+                          int64_t n, int64_t st, int ns, double m)
+{
+    (void)r; (void)h; (void)p; (void)n; (void)st; (void)ns; (void)m;
+}
 int on_scheduler_join(cluster_t *c) { (void)c; return 0; }
 int add_apiserver(cluster_t *c, char *n, endpoint_t *e)
 { (void)c; (void)n; (void)e; return 0; }