ci: report GC and system metrics
ci: report GC and system metrics

The metrics reported are:

- ocaml_gc_allocated_bytes
- ocaml_gc_major_words
- ocaml_gc_minor_collections
- ocaml_gc_major_collections
- ocaml_gc_heap_words
- ocaml_gc_compactions
- ocaml_gc_top_heap_words
- process_cpu_seconds_total
- process_start_time_seconds

Signed-off-by: Thomas Leonard <ea62ade398c3addd3bcc52285a00e98f3b0c618f@docker.com>

docker/datakit,docker/datakit,docker/datakit